I recently turned 20 years old and wanting a fashion change.?

I'm quiet, but yet into my studies. I don't go out a lot and go clubbing. I mainly stay by myself. People say that i look 16 years old, and I don't want that to happen much. I'm the oldest out of five. What kind of stores do you guys recommend? I am a college student so, no expensive places. I don't skate, snowboard or rock out. Does this question make any sense? haha