What are the advantages to the different types of deadlifts? How many types should I do in one workout?

Different variations place stress on different parts of the body - eg stiff leg variety emphasises hamstring/glute involvement. I'd only ever do one variation in any given workout - they're a pretty demanding exercise, and potentially dangerous if your form starts getting sloppy because you're overdoing it.

For an over all workout what give you the bet bang for your buck?

I'd say regular deadlifts. Learn them, then once your body gets used to them start switching up w/ straight leg, sumo, etc.

i found a great variation on by a trainer named chad waterbury. its called a waterbury walk and i fing it works great for strengthening the muscles involved in BJJ. You deadlift a weight equal to 150% of you bodyweight, or work up to it, walk two steps forward to a rack and set it thigh high on the rack, do a rack pull with it and walk two steps back and set it down. repeat 2 reps for 3 sets. it builds great upper back and lower back strength, legs, traps, biceps and great for stronger grip. you never perform a deadlift movement in real life (pick something up and put it down), this movement is more functional because it involves picking up and walking around (carrying heavy objects in everyday life or picking up opponent and slamming him down). try it out and see if you like it.