Yeah I think summer dresses usually work really well. In general, the best outfit is one that doesn't overshadow a girl's natural beauty. A lot of girls don't realize how beautiful they really are and think they need to freak out about what they wear because it defines their image. I'd just say the girl should be the important thing, not the outfit.
I like when girls wear jeans that fit just good, not too loose, something just less than skin tight with speghetti strap shirts or low V neck styled shirts for winter time. Sometimes low cut jeans are very attractive.