I wear plain black bike shorts and a plain Pearl Izumi grey jersey. I used to wear boxers and gym shorts when I was just starting out, but I quickly learned that bike shorts are much more comfortable. And make you look like a real bike geek too.
As far as shoes go, I wear Diadora Gekos. They aren't the best, but they certainly work for me. The supposed best shoes are Sidi Dominators, but I can't speak for them.