A long sleeved shirt, scarf, jeans, boots. Something casual, not to show off, but not the look like you just threw something on from your closet, also show a little color, as to make the outfit not boring
Honestly if your not dressing comfortable and stylish to YOU then your not dressing "cool" that word doesn't even have a meaning anymore. Coming from another Freshman girl just hang out with a group of friends with the same interests of you, I'm sure there's someone out there who likes the same stuff you do. Just don't try to dress "cool" dress you.
Okay, I'm a freshman myself, and I know from personal experience, that you shouldn't try to fit in. Kids are brutal, they don't care an ounce about you. You try to fit in, they either laugh at you, or take advantage of your vulnerable side, and basically push you around. If you have a couple really good friends, that's all that really matters. And if you really want to know, just don't really 'standout', when I say this I mean, don't where something that you've never seen a single person where, because there is bound to be comments. This is, only if you care. If you don't care(which I highly support), then do as you wish. No one's the boss over you, and if they ask 'Why are you wearing that?' your reply should be somewhere between "Because I want to" or nothing, just walk away. Hope this helps!
Changing you clothes will do little if you are not confident. You say you are shy. are you walking around kind of hunched over, like you are trying to hide? If so stop that. Raise your head up and walk like you have meaning and importance. Nothing is more attractive than confidence. If someone says Hello say it hello back with a smile. I know it can be nerve wracking, you just don't have to show it. I have friends and family tell me they are not like me because I am confident. I'm not. Half the time I am shaking like a leaf inside, but I don't let others know. Just fake the confidence and others will soon the great person you are.
You can buy "Seventeen Magazine" or any fashion magazine for cute outfit ideas. You can walk around the mall, look at the windows, in the stores, or just look at the clothes girls are wearing. Not every trend looks good on everyone, so pick a couple and mix it with the things you already have. Being uncomfortable doesn't help confidence, wear what feels good.
Fitting in sucks! I am also a freshman I tried fitting in one time in my life back when I started middle school. I hated it! All of the cookie cutter kids are so boring, just be yourself. It's much more fun that way. I also found that when I stopped trying to fit in I found friends that I enjoyed hanging out with and that I could relate to. I couldn't relate to the kids that 'fit in' because we had nothing in common.