How to make jeans and a t shirt look nicer?

I'm going to high school in the fall and I've got a whole new style! It's a lot of forever 21 type stuff. I bought a lot of t shirts, skirts, and jeans. I got skinny jeans and some regular jeans. How do I make the jeans with a graphic tee a bit dressier? My new style is nicer and organized, like I'm actually trying to look good. I have jewelry but how do I make it look better because to me it looks like boys clothes.