I like the deck! It feels just a bit slow for modern, however. I'd try lightning bolt as a good burn spell, as well as some good one-drop vampires. If you want more ideas for vampires, feel free to take a look at my deck B/R Modern Vampire

Captivating Vampire would be good in here.

How to build a Sacrifice Engine in 3 Steps (chapter 3 guide to the black mage)

1.- Source of Sacrifece Fooder

2.- Free Sacrifice efect

3.- Profit??

Source of sac fooder

the two normal ways of getting creatures to sacrifices are recursive creatures and constant token generation. vampires got access to both thanks to Bloodghast and Bloodline Keeper  ^Flip Since you are in red (and thats the theme of your deck) you also can steal your oponents creatures thanks to cards like Act of Treason

Free Sacrifice Effect

sacrifices effects that cost mana or requires your creatures to Tap, will not do the job. you need tu sac as freely and as many times as possible both Viscera Seer and Bloodthrone Vampire are good cards, Bloodflow Connoisseur and Falkenrath Aristocrat finish your curve

Profit

Free Sacrifice Effects are usualy small and hardly make a big impact on the game. thats why the most important part of the combo is the Death trigers, anything that givesyou advantage each time a creature dies Blood Artist is a personal favorit

i supoce your deck is relatibly budget and maybe only de cards you posess so maybe Bloodghast and Falkenrath Aristocrat are out of reach. but you should at least tray to get

4x Blood Artist

3(or 5)x Act of Treason

2x Viscera Seer

And At least one more boardwhipe

you got to much removal maybe just keep the instant speed ones and the steal and sacrifice efects

Bloodghast is well worth adding from playing against it I can tell you it's a card advantage headache. You pretty much have to exile it or it'll be back in no time. Having it discarded makes it all the more laughable. Definitely a bummer when the only viable target for Inquisition is ghast or if they have a choice and they choose to discard it.

I'd look at Olivia Voldaren as a 2 of in the 4 mana spot for her ability to ping to kill blockers etc...

2 things: Bloodghast is amazing and hard to kill so you might try him out. Also Vampire Nocturnus is amazing and can win games also if you have fetches with him then you can shuffle your library to try and get a black card on top.

Might i suggest Vampire Nighthawk best 3cmc vampire you'll ever find and also pretty insane when combined with Stromkirk Captain.

Terminate is the best kill spell you can find in Black/Red.

Crossway Vampire Is pretty good, i'm still play testing her but she lets your vampires get through. As others have mention Bloodghast is amazing and pretty hard to kill unless you exile it. Rakish Heir is pretty good in any vampire deck.

You have some loose cards in here such as Faithless Looting and Killing Wave. One of them puts you down a card, and the other one gives your opponent too much choice.

As for things to add, the one card that I haven't seen mentioned here is Gatekeeper of Malakir, which is a very strong card.

This looks fun but it's not quite there. There are a few things that I think would help speed you up a bit and help push your clock forward a few turns.

Lands:

your land base seems a bit wacky and I suspect that is because you just took all the lands you had and threw them together? There are a few things that could be changed to help you get everything you need on time. The first thing I noticed is that you don't have to go from (R) to (B)(B) to (1)(R)(R) so you could afford to play less split lands and more basics. Things like Evolving Wilds and Rakdos Carnarium I would take out alltogether for basics. From there you should add in the 4th Dragonskull Summit and try to get up to 4x Sulfurous Springs mainly because those are going to be the cheapest duals that are actually playable. That should set you up to be in a better place. After that I would invest in Blood Crypt before Graven Cairns and probably Blackcleave Cliffs before the cairns too.

The main deck:

I would say you should drop these;

4x Blood Artist because you have no synergy with it and all its really doing is slowing you down. If you are planning on adding in the Bloodghast+Skullclamp then that's another story. But it's not a cheep one.

3x Devour Flesh sure it gets around indestructible but at what cost? if they have more than one creature on the battle field its pretty much useless and you really don't want to be giving them back life, especially with creatures like Vampire Lacerator

2x Bloodline Keeper  ^Flip He Just doesn't really fit into an aggro deck. hes a 4 manna drop that doesn't do anything for you or hes a conditional 5 manna drop, which is too slow in my books.

Now if I count correctly that gives us 8 open slots. You will probably want to replace your lost kill spells and I would suggest 3x Dismember. It's more than Devour Flesh but it's also way better. that gives us 5 more slots. 4x Guul Draz Vampire should help speed up your clock more than the Blood Artists ever could. This leaves the two spots for finishers. Vampire Nocturnus is the go to, and that's because he is good. With only 8 non black spells he has a very good chance of going off.

all of this can be done for about 20 dollars and when you are taking out about 20 dollars out the net value of that deck should satay about the same.

other good spells to consider:Kalastria Highborn, Gatekeeper of Malakir, Falkenrath Aristocrat.

I agree with your suggestion oakenshild for the most, but just one thing how do I deal with hexproof without Devour Flesh. And on the lands, cairn as a one of, is nice especially for double black costs on Sign in Blood, (sorry can't seem to get Night's Whisper), Vampire Nocturnus and Drana, Liberator of Malakir. and adding to painlands more i could afford currently but the shocklands i can't at the moment. And finally this deck is used in mtgo primarily, where some off the cards listed by you aren't that cheap.Also can't Grasp of Darkness replace Dismember or even Urge to Feed which will open 3 slots for sideboard. which i don't what tu putn maybe a third Vampire Hexmage, a third Disfigure and a third Smash to Smithereens

oh wow, crazy, some of those cards are more expensive on mtgo.

oh ya, definetly keep the one of Graven Cairns if you already have it in, it's good. I only meant to say the you should eventually put the good lands in. The pain lands and buddy lands should work fine for the most part. I would invest in the Blood Crypt and Blackcleave Cliffs before I would invest in more cairns. But now that I'm looking at how much the cliffs cost maybe not those ones...

I hadn't thought of Devour Flesh that way. It probably is you best bet against hexproof though. Tribute to Hunger could also be good and Diabolic Edict and Cruel Edict are just straight upgrades.

Dismember is really good but if its not budget enough (wow 2+ dollars online that is actually crazy) then you could put any of the ones above back in. if your gonna keep them in I would suggest you put in some of the above spells in the side board so you can deal with hexproof.

Unless budget is an issue Dismember is much better than Grasp of Darkness and Go for the Throat. It kills bigger things like Reality Smasher, and can be cast for only 1 mana. I'd take out 2 of each personally, since Go for the Throat is generally better, but is dead against Affinity. Terminate would be my choice to fill up the other removal slots over what you have now, but it is also a bit pricey comparatively.

I don't believe Diabolic Edict is modern legal? Tribute to Hunger is a solid option, but I like Devour Flesh over Cruel Edict at least, instant speed let's you bait them into playing more auras before you kill their guy during combat. However as a previous poster suggested, Gatekeeper of Malakir is better than all of these, and possibly deserves some mainboard slots even due to its potency against all creature decks, but especially Eldrazi.

I think you want the playset of Vampire Nighthawk, card is just too good in so many matchups, and is never really a dead card. I'd cut some of either Pulse Tracker or Guul Draz Vampire, both seem a bit eh.

Finally, I think you want more Duress and some Nihil Spellbomb, and maybe even Memoricide, in your sideboard to help deal with combo decks, which seem tough for you otherwise.