If you're playing black, a card I would HIGHLY recommend would be
Vampiric Rites. It is a mana activated ability (so you can use the effect whenever you want as long as you can pa the cost), you create your own sacrifice engine, and it gives you card advantage early in the game. Also if you use it on creatures such as
dark revenant then you can keep drawing cards off the same creature's demise. Also here's a nice little trick that might help you out in the future: a creature with undying can not come back a second time if it died with a +1/+1 counter on it. So
Korozda Gorgon would be a good choice for this deck. She has a solid body and she can remove the +1/+1 counters off of creatures that have already died once. This way you keep a strong front-line as far as your creatures go. It'll make for some really good combos. Also
Undying evil is one of my favorite cards from innistrad, it's always worth giving a test drive.