Nice deck choice! MBD has won me tons of games, but it can vary wildly based on budget and your group's meta. Thankfully the shell is so versatile that it's easy to construct a deck that is fun, strong, and relatively inexpensive (I like to keep my decks <$50). Anyhow, my thoughts on your current build:
Ditch the Dark Rituals. They are dead draws most of the time, and are only useful to power out a game-ending Exsanguinate.
Too many sacrifice spells that hurt your gameplan. You'll demolish your board and weaken your Gary triggers. Another poster mentioned it, but consider Plaguecrafter instead of Barter in Blood. It'll lower your curve a bit and nab a planeswalker from time to time.
Too much card draw. I usually run about four draw spells, which has been sufficient. I really love Read the Bones
Enjoy the infinite combo of Slimefoot, the Stowaway + Parallel Lives + Ashnod's Altar.
Here's what I'm running currently:
16x Swamp
4x Vault of Whispers
4x Darksteel Citadel
Creatures (21)
4 Cuombajj Witches
2 Darksteel Myr
2 Gonti, Lord of Luxury
4 Gray Merchant of Asphodel
4 Phylactery Lich
1 Ravenous Chupacabra
2 Sangromancer
2 Vampire Nighthawk
2 Gonti's Machinations
3 Pestilence
1 Haunted Crossroads
Sorceries (9)
2 Battle at the Bridge
3 Exsanguinate
2 Read the Bones
2 Syphon Mind