Somehow I don't think it's a good idea to take fashion advice from apes...
I usually dress in a way that's appropriate for the event but comfortable. I've worn something like a V-neck knit top (maybe w/lace or ruffled edging) w/knit or stretchy slacks, so it's something I can move in but look nice enough for the event. I may dress it up w/jewelry but not long dangly necklaces or earrings so nothing ends up accidently catching on something or hanging in front of the lens!
I've usually worn black/dark colors so I blend into the background; for a photo booth that may not be necessary. I personally couldn't work in a jacket, I'd find it too restrictive, but have worn a vest especially if I wanted some extra pockets.
Do you know any parents who are chaperoning? Do they dress up much? I wouldn't think it would be necessary to dress up as much as you might for a wedding, but I don't know what's the latest for working a prom or school dance.
(And I don't think I really want to know about prom fashions! lol)
And gaucho is a Steely Dan album, geez...
And you might be out of (your) mind by the end of the prom!