With your age group I think snickers with long socks that go below knees, short shorts White girl tshirt, maybe with a pink design on it. Breathable jacket with no selves over that. Cut hair to punk rock chick and everyone will think you to cute and hot
I think that a nice pair of combat boots are a must for fall, or boots in general. I have fallen in love with my black side zippered boots from Aldo. That paired with a comfy classic sweater, a scarf and skinny jeans. Or you can dress it up more depending on your day schedule.
If you ever are curious on fashion though, I recommend pinterest. com for visuals. :)
I agree with LittleSally. Depending on were you live though it couldn't hurt to go with a light jacket that has a fur coller. Same with the boots. I live in San Diego so fall here can be a little cool since I'm near the coast.