Can someone please help me! fashion crisis, girls!?

i'm in high school and i really want to start looking nice instead of dressing like a usually do- tie my hair in a messy ponytail and wear anything that doesn't have a deep stain and doesn't smell. i know- pathetic! this year whenever i look around everyone went from drab to fab and i like stick out- in a bad way. can someone please give me some clothing I can get from wal-mart or target or old navy under 15 bucks?!? I'm just a teen- my allowance isn't that high!