I do not care what the lady wears. They can look as sexy in sweat pants as they can in thigh highs and lingerie. I always say just wear what you are comfortable in. I have been told that put undo pressure for the lady to come up with an outfit. The ladies do not believe that I am a low maintenance fucktard with 1.3" of dangling death.
An attractive girl really can't go wrong - the girl always makes the outfit. So assuming the girl is, I can get immediately happy to see a well fit t-shirt and jeans, barefoot, with hair down and not up in a pile.