Marcuss,
Just as a starting point, at least one or two isolated rooms would be useful in your situation, if you have the space to do it, so you can record drums and perhaps one other acoustic element live together. There are workarounds for every situation, and most home studio owners have to make them, but iso rooms sound like a good thing for you. Of fousre, before building a room or rooms, do some extensive research as to how to do it - what the shape of those rooms wants to be, what kind of walls, and windows if you have them, height of celings, etc.