Okay...
Going standard legal is good. But that means the only legal Sorin you could use is Sorin, Lord of Innistrad, which would require you to splash white to even play him. There are numerous options to run with though outside of him. If you're wanting Planeswalker power, sadly R/B isn't sitting on anything THAT substantial (outside of Liliana of the Veil).
If you're trying to compete in FNMs, you'll definitely need to refine the list to drop a LOT of the 1-offs.
Ideally your one-drops should include Stromkirk Noble and Pillar of Flame. If you're wanting to go more aggro, then you can add Vexing Devil or, the more likely to have 4x of would be, Rakdos Cackler or Reckless Waif. None of the other three options at the one drop help with the flavor or really fit the overall scheme, but if you're trying to aggro it out, they work. Alternately, Legion Loyalist could prove useful in later game scenarios.
At the two drop, I've found the most useful vampire is Blood Artist. It makes opponents hesitant to engage in combat or otherwise use removal until it's off the board. This can be REALLY useful if you focus a lot on removal, as every creature to hit the yard is essentially an extort trigger. When paired with Stromkirk Captain, the artist can at least be a little blocker and, in some circumstances, can actually be pretty good in combat (typically if you drop Vampiric Fury) - there isn't much out there as satisfying as blocking a Geist of Saint Traft with a Blood Artist and killing the GoST. Other items at the two drop should be more removal based - Searing Spear, Ultimate Price, Mizzium Mortars, Dreadbore, Devour Flesh, etc. Vampiric Fury is another trick to have at the two-spot that most people wouldn't expect.
At the three drop, the only two vampires worth anything are Vampire Nighthawk and Stromkirk Captain. Ideally you can be playing multiples of both as a pumped Nighthawk with first strike will likely win ANY combat (hooray first strike and deathtouch). Other than that, you could splash the odd removal like Murder, but odds are you have their creatures pretty well covered with your two drop removal spells. However, I would advise Rolling Temblor in the sideboard to deal with hexproof stuff - that or Glaring Spotlight.
At the four drop is where your wallet is likely to take a hit, as both Olivia Voldaren and Falkenrath Aristocrat are quite expensive to pick up. You'll see in my build that I use one Olivia and a few Bloodline Keepers. I can see the inclination toward Vampire Nocturnus, but I would argue he actually ends up telegraphing your plays to the opponent. They get to see your top card, so in the event you're top-decked, they can play around whatever you end up drawing.
Realistically, I wouldn't aim for anything higher than a four drop. One of the strengths/weaknesses of vampires is that there really isn't anything at more than the 4-drop that you'll want to be hitting. It's better to drop a Nighthawk/Captain and a Blood Artist/removal than anything you would for five.
For the sorceries/instants, see the ones I listed above. You'll want removal and Sign in Blood - as getting those added few cards can be huge. In the sideboard Act of Treason and Bloodthrone Vampire make a convenient to take the opponent's creature, hit them with it, and then sack it before it returns to their control. But this is hardly something you want in the mainboard to use every game.
I'd actually suggest dropping almost all the enchantments. Seldom will you really want to use one as they create easy opportunities for the opponent to hit you 2-for-1 style. Perhaps some Stab Wounds or Dead Weights to give some removal options, or perhaps an added few damage.
For the lands, you're spot on that Dragonskull Summit and Blood Crypt are pretty much a necessity. I'd also suggest trying to pick up 2-3x Cavern of Souls. You can name 'vampire' and it does the mana fixing AND prevents counters against your creatures. Lastly, I've had some success with Rogue's Passage paired with Stromkirk Noble in late game situations to ensure it can get a few hits in and grow.
Anyway, obviously this isn't the only way to build it, but I've had some pretty good results with my build. It's not prohibitively expensive and will lose to the upper echelon decks, but I've enjoyed the flavor of it.
Good luck building and playing it.
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