Well, it really depends on how many sets of clothes you want to have. Most games I've seen, they used a completely different model for each different set of clothes (minus the head in some cases). You are going to have a lot of clothes I recommend you make a basic set for each type you need and texture those differently (thank god the edit button works).
For example you have a character creation set up where you can choose the kinda shirt your character will have. Lets say you want to have around 30 different shirts, well these will fall into 6 basic catogories: short sleaved, long sleaved, long sleaved with the sleaves rolled up, dress shirt, dress shirt with sleaves rooled up, and sleaveless. Just make 6 different models and texture them acordingly.
The only time I would model seperate clothing for models to wear would be if you wanted to show them putting on that clothing, and even then I would switch it with one that was modeled with it already on afterwards, to reduce polygons. I hope that helps.
Am I a butterfly dreaming I'm a man?
Or a bowling ball dreaming I'm a plate of samishi?
Never assume that what you see or feel is real.