Suggestions for lands:

If you want to stick to a high number of basics I would recommend using Check lands, Battle lands(listed in typed-lands section), Bond lands, and/or the Filter lands.

Check Lands:
Sunpetal Grove
Glacial Fortress
Hinterland Harbor

Bond Lands:
Bountiful Promenade
Sea of Clouds

Filter Lands:
Wooded Bastion
Mystic Gate
Flooded Grove

If you are willing to spend more money in order to do more deck thinning and have probably slightly more reliable color fixing you can use the typed 2-color lands with fetch lands and typed land tutors.

Non-basic Tutors:
Ranger's Path
Skyshroud Claim
Farseek
Nature's Lore
Hour of Promise

Fetch Lands:
Windswept Heath
Flooded Strand
Misty Rainforest

Shock Lands:
Temple Garden
Hallowed Fountain
Breeding Pool

Battle Lands:
Canopy Vista
Prairie Stream

Cycle Lands:
Scattered Groves
Irrigated Farmland

Original Dual Lands:
Savannah
Tundra
Tropical Island

Overall thoughts:
Can definitely tell this deck hasn't been touched in years. Goal with my suggestions below are to try to help it play more reliably, do what it wants to do a turn or two earlier, and add sustained power through more card draw options. Sorry in advance for the wall of text. I hope you're able to find it helpful...

Suggestions for addition:
https://deckbox.org/sets/2219553?s=c&o=a

Overall design suggestions:
Landbase - Get it back up to 36 total, swapping in Terramorphic Expanse for Rupture Spire is just a straight up 1 to 1 upgrade. You're missing two of the three checklands you could be running.(Sunpetal Grove and Hinterland Harbor.) Not a huge fan of Novijen, Heart of Progress in this deck since you don't run a ton of creatures and this is a go-deep strategy deck, not a go-wide.

If you wanted to invest a little bit more into the landbase, you could add in more of the dual lands that're forest-typed and then run Skyshroud Claim and/or Ranger's Path. I'm thinking of the Shocklands (such as Temple Garden), Battlelands(such as Canopy Vista), and Bicycle lands(such as Scattered Groves)

There's the general list of cards that would be useful no matter what way you took the deck in this post and then in a comment under it I've included lists for cards I think would be especially good if you wanted to lean into an equipment package or an aura package. I personally think the aura package is probably a little stronger due to all the card draw options it has but would represent a big rework for the deck.

Suggestions for card cuts:
Mikaeus, the Lunarch - This card doesn't play to the commander's strengths. Good in go-wide, not go-deep.

Rune-Tail, Kitsune Ascendant - Generally good but isn't part of the focus of your deck.

Wall of Denial - Generally good but isn't part of the focus of your deck.
Teferi, Mage of Zhalfir - This guy is great control but he's a lightning rod for kill cards and he doesn't really contribute the deck's battle plan.

Tolsimir Wolfblood - Better in a go-wide strat deck. I don't think he brings enough to this deck to justify a CMC6 slot.

Vigor - This guy isn't so much bad as it's just sort of weird in this deck. I feel like you really want to have AoE burn in your deck to abuse this guy. Seems like other cards would help more.
Simic Sky Swallower - This guy's pretty alright but I feel like I'd rather have Sigarda, Host of Herons, Bruna, Light of Alabaster, or Heavenly Blademaster in its place.
Artisan of Kozilek - Honestly not sure how I feel about this guy. The Eldrazi fatties are great but I feel like their place is in decks that cheat them into play during the early game like a reanimator style deck or Mayael, or something.

Ulamog, the Infinite Gyre - Same as the above Eldrazi.

Tribute to the Wild - I like that this card is a 1-for-many design but I feel like allowing your opponents to choose is a fatal flaw, especially in a deck that doesn't benefit from the fact that your opponents are sacrificing things. (Unlike in a Mazirek, Kraul Death Priest deck or something.)
Resounding Silence - There are far more efficient cards for similar effects. It's thematic but it'd probably be one of the first cards in this whole list that I'd cut. To be specific, Path to Exile, Swords to Plowshares, and others cost less mana and aren't conditional on the creature being attacking.

Day of Judgment - Not a huge deal but if you're looking for every opportunity to improve the deck, Wrath of God or Supreme Verdict are strictly an upgrade.

Fated Retribution - Honestly, I have a hard time stomaching a CMC7 wipe. I barely run Austere Command because it's CMC6. Personally, I'd be looking to slot in Cyclonic Rift or Supreme Verdict here. If you REALLY like that it's instant speed and don't want to lose it, consider running Rout instead so at least you have the option to spend less mana on it. Maaaaaybe worth adding back in if suddenly we have 2-3 people with superfriends style decks with tons of planeswalkers...

Praetor's Counsel - Just don't think this card does enough in this deck. Better card if you're constantly intentionally filling up your graveyard imo.

Prophetic Prism - This is underwhelming in a deck that doesn't get value from just having artifacts on the field. The mana fixing it enables is easily overcome with just a slightly more robust landbase.

Darksteel Ingot - Personally I'd be looking to cut this for one of the other Signets since they can come out a turn earlier. This rock isn't bad, it's just not great either.

Aura Shards - You're not running a lot of creatures and you're not playing cards that produce tokens. I honestly think this card is pretty lacklustre in this build. I would use something like Trygon Predator as an alternate repeatible removal or just go with a cheap 1-time use like Nature's Claim if you don't want to lose the artifact/enchant removal. Alternatively, you could lean into it as a subtheme and add cards like Sword of Body and Mind, Verdant Embrace, Raised by Wolves, Sigil of the Nayan Gods, etc... but that's sort of counter-productive since Rafiq's whole shtick is to have a single creature attack for loads.

Indestructibility - Decent effect, decent synergy, just feel like it's just decent and not amazing. Maybe suggest cutting this after you've made other cuts. I think there are cards that would just help your deck more than this.

There are other cards in here that're solid like Jenara, Asura of War, Empress Galina, etc. but you might consider cutting them if you decide to focus the deck on an equipment or aura theme. My recommendation is that you probably want to focus the deck a little more on the Voltron aspect as opposed to legendary toolbox. If you like the toolbox aspect of having Captain Sisay in the deck and a bunch of legends appeals to you, maybe it'd make more sense to build a Captain Sisay toolbox deck as opposed to shoe-horning it into a Rafiq battlecruiser deck?