Dont worry about high school in itself much because it will be over in two years. If anything you should be thinking ahead about college, assuming you will be going. Your good friends now will still be when high school is over. You will drift away from some. Thats normal. Actually, I'm a little envious. These days you have social networking, IM and video cams. I didnt and I pretty much lost touch with everyone. If a great friend moves a couple hours away, and you both liked gaming while in school, you can both still get together and kick a*s against zombies.
As or styles and such, think about what looks good to you. Not passable or ok... but good. Black T-shirts are very casual. Same with faded bluejeans. But school isnt a farm. Well... actually *good* black shirts and unfaded jeans can look cool so long as they arent heavily outworn and you dont wear Nikes. Youre not Michael Jordon. But dont blow a wad of cash on designer clothes either. People that do are more interested in impressing a clique than anything else.
Semi-casual shirts or well-made T's. Dockers. Newish but comfortable jeans, not stonewashed. Appropriate belts (Dockers-type belts and bluejean belts are not the same) Casual shoes (Reeboks or whatever, just not the athletic white ones) with socks that work with them. White socks dont work with medium brown shoes. A couple of full-button shirts in nice subtle colors for the dressy occasions. My fav dress shirt is a medium dark subtle green with a black tie. Looks much better than a white shirt.
Subtle colors are always good. Dressing entirely in drab earth tan colors or all black/gray is boring. And... I must say it... wearing a T-shirt with Enterprise on the front to school isnt a great choice either. Much better places to wear it at. Oh and as for colors, also consider looking at some that work with your eyes. Dont laugh. I know thats usually said for girls but if it looks better so what?