I chose "whatever he or she wants". While I get that the traditional wizard or sorcerer is often seen wearing something between a robe and a bikini, it really should depend on a combination of the race, culture, location, and character's preference. A wizard in the jungle probably won't be wearing a robe, and might be indistinguishable from any other explorer. The same goes for a spellcaster in a cold region; she is probably piled under enough furs to equate to leather armor (which it very well could be depending on how armor affects spellcasting). In fact I think that in most cases where a spellcaster is out adventuring she should not be clad in a robe (or revealing outfit).
|Frankly, none of these guys are dressed for the occasion.|
Baby steps, I guess.