Great :)
Okay first he wouldn't be able to do anything big with out ingredients and tools, herbs, bones and of course dolls, the most he could do with out being prepared would be able to speak to voodoo spirits and control his own shadow, it being a part of his soul. With tools he'd be able to make voodoo dolls that could effect others, but that takes time and he'd need a part from the person or thing the doll is suppose to be, very minor alteration to things, like changing a jack of clubs to an ace, and he be able to do some necromancy though that like a doll requires time to do. He'd also be able to make deals for people with voodoo spirits though that is less of a power and more of a job for him.