Best advice I can give you is to have as little overlap of races and classes as possible, it will maximize the amount of content you will be able to experience in the game.
I admit content maximation is on my mind. I don't want to miss out on experiences! But from reading experiences in the forum, I got the idea that different branches of the story are mostly traversed by choosing between good and evil, not so much race or class. But I might be mistaken...
Race and class will certainly influence combat, so at least for the full martial/magic experience I will try to try for very different races and classes.
