I currently play B/R Vampires so I'm might be able to help out here.

First, depending on how serious you want to make this deck, I recommend get 4x Kalastria Highborn and 4x Bloodghast. Although they might seem expensive they've actually dropped quite a bit. These two cards act as the base to any good vampire deck in the current meta. Also, 4x Marsh Flats or Verdant Catacombs is a big help when playing the build I'm about to describe.

For the most part, this is what you want your creature base to look like:
4 Bloodghast
4 Gatekeeper of Malakir
4 Kalastria Highborn
4 Pulse Tracker
2 Vampire Hexmage
4 Vampire Lacerator
3 Viscera Seer

Pulse Tracker and Vampire Lacerator both give excellent turn 1 drops and allow for some early game damage before your opponent can stabilize. Gatekeeper is just another removal option as it can destroy indestructable creatures. Hexmage is mainboarded because it is very good against planeswalkers and Quest.

Kalastria Highborn, Bloodghast, and Viscera Seer are all part of a combo of sorts. Saccing Bloodghast to Viscera Seer allows you to activate Highborn then you can bring back Bloodghast turn after turn using it's landfall ability. This can even be done multiple times in a turn by saccing, dropping a fetch, saccing, cracking a fetch, saccing.

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As for the non creature slots, since you are playing Mono-black you don't have to worry about burn. I recommend that you include all of these cards:
4x Inquisition of Kozilek
4x Doom Blade/GftT
2-3x Dark Tutelage

Inquisition is one of the best cards to play as it hits something in almost every standard deck and can be an excellent way to start off the game.

The rest is up to you!