There aren't really any vampire guilds. There are 3 vampire clans, sort of at a power stuggle and the other 2 clans that you aren't a part of will attack you on sight. The vampire clan you're apart of (the one that attacked and infected you) will attack you too, because they see you as an unpure vampire. The way you were made. You can do quests for certain members of your clan and get on their good side, but you can't become head of the clan as you would in a guild. The real benefit of being a vampire is the stat increases. Which one clan is really good if you're a monk type fighter.
I kill two dwarves in the morning, I kill two dwarves at night. I kill two dwarves in the afternoon, and then I feel alright. I kill two dwarves in time of peace and two in time of war. I kill two dwarves before I kill two dwarves, and then I kill two more.
I may be bad, but I feel good.