I'm Vegas born and raised, so I know the fashion around here. For the day, bring shorts, mini skirts, cute sundresses, tank tops, and sandals. It's really hot here in June, and the Strip is a few miles long, so you'll want to be comfortable when walking it. For the evening, a sexy cocktail dress and heels should do the trick. Sparkley things are typical here, such as sequined tank tops or shiny shoes and jewelry. We don't wear anything particularly special here. All the girls wear normal summer fashion. Also, bring a bathing suit. I promise you'll want one.
Enjoy your stay.