Consider:
Dockside Extortionist - A way to play more of my 5-drops, but probably too easy to abuse
Boromir - Another Selfless Spirit that also stops free spells
Myriad Landscape - More ramp
Invoke Justice - Reanimate anything or get back a sac outlet, and go infinite with Dualcaster+Hofri+outlet
Mistmoon Griffin - Goes infinite with Hofri + outlet
Coercive Recruiter - Can Threaten multiple times if I have other pirates. Another infinite with Kiki
Captivating Crew - Repeatable Threatens
Felidar Guardian - Infinite with Kiki, and re-use ETB effects
Skullclamp - More card draw. Even if my things don't naturally die to the clamp, I have enough sac outlets to make this a card advantage machine.
Deflecting Swat - Protect Hofri from spot removal, or counter a counter
Fury - Semi-sweeper that turns into a really scary body
Quintorius, Loremaster - Make spirit tokens, sac spirits, and get back cool spells
Big Score - Draw, ramp and discard, but at 4 CMC it might be too slow
Tormenting Voice - Early filtering
Seize the Spoils - Card draw, discard outlet and ramp
Electric Revelation - Early filtering, and a bit of card advantage later
Tibalt's Trickery - Counterspell, but they're guaranteed to get something else
* Rip Apart - Cheap and very flexible spot removal
Rally the Ancestors - With enough mana, this can reanimate a bunch of stuff, and then just sac them before they get exiled
Combustible Gearhulk - I might not have enough expensive things for this to be likely to draw me cards, but it's still a good body with an ETB that does something, and it could fill my yard for "reanimation"
Ranger-Captain of Eos - Tutor up Esper Sentinel (or a mom if playing those), and can sac for a opponent-wide Silence when I’m ready to go off
Makeshift Munitions - Sac outlet
Kor Cartographer - Always ramp and maybe fix, but at 4
Divine Reckoning - Sweeper that keeps Hofri alive
Cosmic Intervention - Protection that also triggers ETBs an extra time
Drogskol Cavalry - Lifegain whenever I get a spirit, plus a big hasty flier and a mana sink that makes 2/2 hasty fliers when I have Hofri, but it costs 7 mana to play
Aurelia - Play her for an extra combat, then sac her for a third (and potentially infinite combats with the Karmic/Reveillark loop)
Archangel Avacyn - Protection for my board, and then it can be a sweeper for small things more or less on demand
Restoration Angel - Blink something to re-use an ETB or protect from spot removal, but only if it hasn’t died yet. Does go infinite with Kiki though
Charming Prince - Blink something to re-use an ETB, or just get some minor value otherwise
Flickerwisp - Get extra value from flickering my stuff, or work as pseudo-removal when it’s on the board
Dire Fleet Daredevil - Snapcaster for their yard
Teferi's Protection - Goes in every white deck
Dawn Charm - A fog that can also be used to protect Hofri, or stop a big burn spell
Archaeomancer's Map - Ramp, but might not do much if I keep doing White Orchid and Solemn stuff
Coldsteel Heart, Fire Diamond, Marble Diamond - 2-mana tapped rocks
Outpost Siege - Get value off of my creatures leaving (when I sac them), or be a card advantage source
Impact Tremors - Get some chip damage for cheap
Barrage of Expendables - Easy to get constrained on red mana,  ut this is a cheap sac outlet to play with a useful effect
Anger - Haste enabler without having to sac things first
Austere Command - The most flexible sweeper
Blacksmith's Skill - Protect Hofri against almost anything
Fiend Hunter - Permanently exile one creature and O-ring another, but requires a sac outlet and Hofri to be worth it at all
Mother of Runes, Giver of Runes - Cheap protection
Benevolent Bodyguard - Protection that can be used right away, but only twice unlike moms
Kami of False Hope - The white Spore Frog, though not as sticky
Kami of Ancient Law - Enchantment removal on a spirit
Moonlit Strider - Regrow a spirit when it dies
Alseid of Life's Bounty - Protect Hofri
Sejiri Shelter - Protection with land drop backup
Vesperlark - Reveillark with everything halved, but might not have enough good targets
Mass Mutiny - Steal a thing from each opponent
Kazuul’s Fury - An expensive Fling that can be a land in a pinch
Moon-Blessed Cleric - Enlightened tutor on a body, but I don’t have a ton of card draw and Karametra is using my only copy
Fury - It might not be able to kill as much relevant stuff as in modern, but the utility is very high, and the body after Hofri is quite relevant
Impulsive Pilferer - Play and sac twice to net a mana, then either bring it back with Reveillark or similar, or encore it when I have Anointed Procession
Frontline Medic - Attack without fear of losing my stuff, and Mana Leak X spells
Thermopod - Sac outlet with a useful sac payoff, but 5 mana is quite a bit
Insurrection - Steal everything, but very expensive
Emeria Shepherd - Expensive, but gives me access to reanimation. Probably not great without green, though
Goblin Dark-Dwellers - Highly dependant on the number of targets
Obsidian Charmaw - Targeted land destruction, and can potentially be very cheap if they have good lands
Yosei, the Morning Star - Big, flying spirit with a good death trigger, but only hitting one player might be a bit too narrow
Hope of Ghirapur - Keep one player in check for two turn cycles
Wispmare - Cheap enchantment removal that puts itself in the yard
Crush Contraband, Return to Dust - Removal
Spirit Bonds - Sac my spirits to protect other stuff, and get spirit tokens when I play creatures
Unbreakable Formation - Board protection or a way to safely attack in a stall
Oreskos Explorer - Get some lands when behind, but only to hand. Works well with Archaeomancer's Map
Lorehold Command - All the modes are nice, but at 5 mana it’s probably going to be difficult to get their full value at the right time
Hour of Reckoning - Sweep the board while keeping my token copies around
Conquering Manticore - 6 mana might be a bit much for a single Threaten, but it does come attached to a big flier
Act of Treason - A baseline Threaten
Grab the Reins - This could potentially be as much as a 3-for-1, but only in very specific cases and for a lot of mana. I will probably usually have a sac outlet available, in which case this is just a 4-mana instant speed Threaten
Lunarch Mantle - A sac outlet that I put on Hofri and which makes him a bit stronger
Idyllic Tutor - Find the enchantment I need at a given time
Enlightened Tutor
Heliod's Intervention - Removal or life gain
Wrath of God - Baseline sweeper
Fumigate - Sweeper with some upside
Sunforger - Get the spells I need
Shelter - Protection that replaces itself
Flameshadow Conjuring - Get temporary tokens of the good stuff
Trading Post - Sac outlet with other utility modes, but it can only sac one creature per turn cycle, and I need to have an artifact in the yard to use it
Hoarding Dragon - Tutor two artifacts
Goblin Matron - Tutor for whichever goblin I need. Probably Kiki, Dark-Dweller Oracle or Cratermaker
Conjurer’s Closet - Blink the stuff I steal instead of saccing it immediately
Scion of Vitu-Ghazi - I probably have some sweet tokens to populate, but this only works when casting it
Forbidding Spirit - A spirit that can keep me somewhat safe for a few turns
Spawning Pit - Free sac outlet, but it doesn't really have a very synergistic effect, so I wouldn't mind cutting this
Claws of Gix - Cheap outlet to play, but costs mana to sac things. Does let me sac an opponent's artifact with ConscriptsInferno Titan - Sweet body to re-use, but is it worth 6 mana?
Harness by Force - Can Threaten any number of creatures, but at full price
Monk Idealist - Get back an important enchantment
Angel of Finality - Graveyard hate
Wall of Omens - Draws a card and can block early aggression, but if I draw it late it’s a Divination at best
Junk Diver, Myr Retriever - Regrow artifacts
Iroas, God of Victory - Makes attacking safe and efficient, but doesn't otherwise synergize much
Archangel of Thune - Good value creature, and can easily get bonkers with soul sisters etc, especially when copied, but probably won't have enough support
Soul sisters, Suture Priest - Get a little bit of extra value from tokens entering
Reckless Barbarian - Ritual with built-in sac outlet that nets RR
Cathodion - Ritual that nets 3 colorless with Hofri + outlet
Generator Servant - Ritual that nets 2 colorless that can give a creature haste, but needs a turn to untap
Goldhound - Tiny ritual with built-in sac outlet, but has to wait a turn
Seething Song - Acceleration
Geist-Honored Monk - Make a few spirits on etb and potentially get pretty big, but requires a lot of bodies
Thought-Knot Seer - Can strip away tutored cards, but don’t want to have to worry about colorless
Mirror Entity - Give all my things haste when I have Hofri, and can even make all my non-spirits die for 0 mana to get triggers
True Conviction - Makes combat much better and gives me some survivability, but 6 mana is a lot
Reliquary Monk - Can kill either artifacts or enchantments, but doesn’t work when there’s a RIP effect
Stonehorn Dignitary - Prevent some scary combats
The Akroan War - Steal something and force attacks, then removal, but it’s slow and costs 4
Word of Seizing - The split second is nice, but 5 is a lot
Nahiri, the Harbinger
Fateful Absence - Cheap removal that can hit planeswalkers
Iron Myr - Mana dork
Curse of Opulence - A kind of ramp, and promotes violence, but there’s not a lot of synergy and it does give away advantage
Windborn Muse - A spirit to keep me safe
Response // Resurgence - Removal or an extra combat
Filigree Familiar - Cheap value creature with both ETB and death triggers
Stonecloaker - Can save something and/or stop a reanimation effect
Elite Spellbinder - Light stax piece, taxing scary cards
Felidar Cub - Destroy an enchantment by saccing itself, but the spirit versions are probably enough
Reckless Reveler - Artifact removal in foil)
Torch Fiend - Artifact removal
War Priest of Thune, Monk Realist - Enchantment removal, but needs a sac outlet to get multiple

Lands:
Hall of Heliod’s Generosity - Get back important enchantments
Slayer’s Stronghold, Sunhome - Utility lands that make creatures better at the cost of being colorless

Sneak attack options:
Sneak Attack - Very cheaply cheat things in, and with Hofri the drawback isn't a problem
Purphoros, Bronze-Blooded - Sneak attack on a big stick
Luminate Primordial - Removes three things
Meteor Golem - Destroys anything
Myr Battlesphere - Can do a lot of surprise damage or generate a lot of blockers
Resolute Archangel - Get back to 40 twice
Sandstone Oracle - Draw cards if I'm behind
Knollspine Dragon - Fatty that can refill my hand, but I need to be able to get damage through before it does anything
Etali, Primal Storm - Surprise hasty Etali is sweet
Hellkite Tyrant - Great when hasty

Consider (probably have):
Goblin Cratermaker - Removal for an artifact or eldrazi, twice. Can also kill small dudes
Selfless Samurai - Protection for Hofri
Valorous Stance - Protection or removal
Pillardrop Warden - A spirit (and dwarf!) that can return an instant or sorcery and sac itself
Goatnap - Basically a basic Threaten
Mage’s Attendant - Access to multiple force spikes
Heartfire, Final Flare - Sac outlet and removal
Riveteers Requisitioner - Pays for itself in treasures, but can then be blitzed back to draw a card and make new treasures for cheap
Hearth Kami - A spirit that can remove most artifacts, but it will close me
Archon of Falling Stars - Reanimate an enchantment on death, but 6 mana might be too much for this despite the body
Spreading Insurrection - Decent budget option, but costing 5, this is unlikely to get more than 2-3 creatures

Consider (don’t have):
* Éowyn, Fearless Knight - Removal and protection
Nahiri's Resolve - Pump, haste, and blink
$ Scalelord Guardian - With Hofri, this is a Sun Titan on steroids
Neyali, Suns' Vanguard - Makes my tokens much better, and gives me card advantage
Venerable Warsinger - Cheap spirit that can reanimate most of my things
$$$$ Elesh Norn, Mother of Machines - Obvious, but it's another 5-drop
$$ Flawless Maneuver - Protect Hofri and the board for free
Traitorous Greed - A cheaper Threaten with the cashback
Selfless Savior, Resolute Watchdog, Dauntless Bodyguard - Cheap Hofri protection
$ Timely Ward - Protection for Hofri that sticks around
$ Song of the Worldsoul - Populate my cool tokens on casting spells
Act of Aggression - Instant speed Threaten
By Invitation Only - Flexible sweeper
Brion Stoutarm - Flinger and lifegain
Shivan Harvest - Expensive to use outlet with great utility
Skyfire Kirin - Every spirit comes with a (slightly restrictive) Threaten attached
$ Grand Crescendo - Protect my board and maybe even make a bunch of tiny tokens
$ Cursed Mirror - Mana rock with nice utility
Séance - Temporarily reanimate things as spirits after they permanently die
Extraction Specialist - Reanimate something cheap twice
$$ Akroma's Will - Protection and wincon
$ Canoptek Scarab Swarm - Graveyard hate and potentially a bunch of fliers
$ Space Marine Devastator - Remove one artifact/enchantment on ETB, another on re-entry, and potentially extras on cast if I have more mana to spend
$ Leyline Tyrant - Decent body that lets me store red mana and can kill something (or burn someone) when it dies
Ruin Grinder - Wheel on a big body that can find a land in a pinch
Angel of the Ruins - Big, flying body which can exile two things, and has plainscycling if I can't get to the 7 mana
$ Robe of Stars - Protection for Hofri
Wrangle - Cheap Threaten with restricted targets
Restoration Specialist - Regrow an artifact and an enchantment, with built-in sac outlet
Nikko-Onna, Yuki-Onna - Spirits that destroy enchantments/artifacts and can be re-used, but might be a bit expensive for what they do
Ronom Unicorn - Cheap enchantment removal
Yavimaya Steelcrusher - Artifact removal
Stonebound Mentor - Decent bodied spirit that scries when I Hofri things
Selfless Squire - Fog when someone swings big at me to get a big boy, then re-use it with Hofri + sac if they try again
Priest of Urabrask - ETB ritual that nets RRR
Space Marine Scout - Ramp
Cadric, Soul Kindler - Get temporary copies of my legends
Odric, Lunarch Marshal - Keyword spreader to hopefully give everything flying
Emberwilde Captain - Become the monarch, and make it dangerous to attack me
Pardic Miner - Slow down the ramp deck
Stoic Farmer - Ramp when I'm behind
Guardian of Faith - Teferi’s Protection on a spirit, except it doesn’t protect me, or itself
Living Lightning - The red Archaeomancer?
$ Rain of Riches - Give things cascade when I use treasure mana
$$$$$ Academy Rector - Can tutor up Anointed Procession, buuut expensive and cannot be doubled unless I already have the Procession
$$$$$ Su-Chi - Ritual-death for 4 colorless, but reserved list and 4 CMC
Angel of Grace - Good-sized flier that can save me from dying twice
Deafening Silence - Slow down the game
Avalanche Riders, Goblin Settler - Targeted land destruction
Catalyst Elemental - Ritual with built-in sac outlet, but only nets a single mana (R)
Ardent Electromancer - Ritual that should net R with Hofri +  outlet, but could add more if I have a warrior
Treasure Hunter - Regrow artifacts
Shimatsu the Bloodcloaked - Sac a bunch of stuff if I can't find a repeatable outlet
Seht's Tiger - Protection from a color which can stop a big attack or even a burn spell, but doesn't help my creatures
Vengeful Ancestor - Goad something
Clone Shell - Can cheat up to two things into play
Treasure Keeper - Get random stuff off the top

Considered cuts:
* Brought Back - An alternative to get back stuff if I don't have Hofri (or get back Hofri if destroyed), but requires that I hold up WW. Does get better with more fetches in the deck
Chaos Warp - I might just have enough other removal that I don't need this risky one at 3 CMC
Song-Mad Treachery - An expensive Threaten that can be played as a land
Wear // Tear - I might have enough of these effects on creatures
Thrill of Possibility - Too weak?
Bitter Reunion - Hand smoother with the option of giving my stuff haste later
Ao, the Dawn Sky - An efficiently costed (for its size) big flier with a good value death trigger, but the value does depend on the number of cheap permanents in the deck. It is a spirit, though
Twinflame - It's here because of Dualcaster Mage, with the secondary option of being able to copy a few things for ETBs, but requires that I already have things going a bit
Reconstruct History - Great value card, but does nothing for the first 3-5 turns
Loyal Warhound - Only works when I'm behind, the body sucks, the land is basic (no fixing) and enters tapped
Hallowed Spiritkeeper - Cheap body that get me a bunch of spirit tokens
Esper Sentinel - No ETB or death triggers, but a cheap source of card advantage, especially when pumped by Hofri
Remorseful Cleric - Reusable graveyard hate on a cheap spirit

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Cuts:
? Burnished Hart - Expensive to use
Boreas Charger - The upside is potentially big (ramp AND guaranteed future land drops/discard fodder), but I can't really get the benefit without a sac outlet
Kari Zev's Expertise - I might not have enough spells to cast for free off this, or enough sac outlets to make use of this early
Firbolg Flutist - ETB threaten with myriad on the borrowed dude, but costs 6
Warstorm Surge - 6 mana for an enchantment that doesn't immediately impact the board, but if I have Hofri + outlet + nontokens out I'll be able to remove something right away
? Quintorius - Makes spirits whenever Hofri does his thing, and also makes all my spirits a bit scarier
Keening Apparition - Cheap enchantment removal that is a spirit
Mana Geyser - I might actually not have that much to dump a bunch of red mana into
Needle Spires - Reanimating this with Hofri is cute, but not very realistic and not worth the ETBT
Vandalblast - Replaced with Ingot Chewer since I never want to spend 5 on overloading this anyway
Dark-Dweller Oracle - I don't want to pay to sac
? Blasting Station - Limited uses, but does kill with Karmic Reveillark, and doesn't cost mana to use