+1 on bibs, but shorts are cool too if that's all you can find.
Don't know if anyone has mentioned this to you or not, but
DO NOT wear underwear under your cycling shorts. They are meant to be worn comando and adding a layer of cotton between your ass and the shorts is a recipie for disaster.
Here is where I get most of my cycling clothes from.
http://www.velowear.com/
Their lower end stuff is actually pretty good. Just look for the solid colors and that's typicllay were I've found lots of value. Depending on your size I've actually found some smoking deals in their close-out sections.