Depends on the gig, Gary. If I was working in places with dirt floors, I'd wear work boots too...but they'd be "dress" work boots (with Yamaha logos)...gotta keep up an image.
Seriously, I usually dress in black, with a black cashmere jacket for the ritzier (and air conditioned) places...black dress pants, or black jeans if it's real casual.
Very few gigs around here you'd wear shorts, unless it's an outside job, like a barbecue or lawn party in the summer...but, I don't do outdoor gigs.
If not sure, keep it uncomplicated, wear pants and shirts that fit you good (no "old man's" bluejeans); but, no matter what you choose to wear, make sure the audience can see you are having a good time playing and that you are confident (and competent) in what you're doing.
Interesting topic.
Ian