Hey, I'm 16 and going into my junior year if high school. I love clothes and literally made my back to school shopping list today. here is my list and the estimated amount of money I will spend plus store recommendations. (I will tweak it to suit it for you because it sounds like you are starting from scratch!)
Tops: Forever21 has great deals and a huge variety! Also try Abercrombie,Hollister, Victorias Secret Pink, Urban Outfitters, Aerie, and my personal favorite, American Eagle. Don't be intimidated by the prices, they always have clearance in the back (sometimes as low as five bucks for a top) and they run sales all the time. Aeropostale is okay for Cami's but it is really more of a transition store for middle schoolers. Stay away from polo shirts, they are not too cute in my opinion. Anyway, here's specifics:
1) 3 plain fitted tees, preferably scoop or v neck. One black, one white, and one in any color you like. I get them at Forever 21 for about $5 each.
2) 3- 4 Cami's. Two lacy and two plain, one black, one white, one navy, and one another color.
3) 3-5 graphic or printed fitted or slouchy tees. These are more fashionable than the plain tees which are more fore layering. You can get them at any store mentioned above. You can probably get them about $15 each. Get then in different cuts and styles, some over sized ones are cute!
4) 2-3 cardigans for layering over a cami or fitted tee. Try to get navy,white, or black so you can mix and match. They usually run $15-$20 at Forever21.
5) 2 sweaters that are a bit oversized in a cool color or print like stripes. So comfy for fall! You can wear these with skinny jeans or leggings. don't spend more than $20 each, usually cheaper at Forever21 or even Target.
6) 5 "fashionable" tops that are just cute and stylish, even semi formal because it you can totally dress up for school. This will be stand out pieces! Don't be afraid of different materials, lace, glitter, big prints and other things that draw your eye. These pieces will run anywhere from $15 to $30 each. They will be cheaper at Forever 21 but I love American Eagle or Urban Outfitters!
7) 2 hoodies, one zip and one pull over. You can even keep one in your locker for when you get chilly. I usually get them at Victorias Secret Pink but they are pricy, around $35-$50. Shop around for sales.
1) 5 pairs of jeans! You will LIVE in jeans! My favorite are from American Eagle or Hollister because they simply fit well. However, quality jeans are pricy (up to $50 which is ridiculous!) so wait for sales and coupons! I got two pairs of hollister jeans online yesterday for $25 each which is a good deal, more than 50% off :) you can get them cheaper at Old Navy, Target, or Forever21 but I think they fit weird and don't last as long.
2) 1-2 pairs of yoga pants from Lulu lemons, VS Pink, or Aerie. Super comfy and they look cute with tees and hoodies. I buy them from pink for $35 each.
3) 1 pair of sweat pants. It doesn't matter where they are from. They are for exam days or days when you are sick. Maybe $20?
4) 1 pair of black leggings to go under skirts or cute tops or slouchy sweaters. $3-$5 at forever21.
Tip: one of your pairs of jeans can be jeggings which are all the style of jeans and all the comfort of leggings! Two of your jeans should be skinny jeans and two in boot leg or flare, all different washes of course.
1) 2-3 dressed depending how girly. At least one casual and one nice one. You will need them for days you feel like dressing up and for presentation days because a lot of teachers require you to dress up. Anywhere $15 to $45
2) 2-3 skirts to pair with those fitted tees. Maybe one black or navy and one or two printed ones. $15 each at Forever21.
1) 1 pair of gym shoes for gym class from pretty much anywhere. Nobody cares about those haha
2) 1 or 2 flats to go with cute outfits like jeans and a cute top, skirts, or dresses.
3) 1 pair of mocs because they are so comfy for fall!
4) 1 or 2 pairs of boots like UGGS which I love!
5) 1 pair if whatever you want like sperrus or Toms or whatever you like!
The price of shoes completely depends on what you buy so you can get really expensive shoes or really cheap shoes.
1) a few pairs of earings that you think are cute, super cheap at Forever21 lime literally $3 each. Same with necklaces.
2) 1-2 belts, at least one brown leather one for jeans and maybe one to wear with dresses. I like American Eagle belts but they are pretty good and cheap at Aeropostale like $10 or $15.
3) 1-3 scarves in cool prints to go with solid color tees or slouch sweaters. Cute ones at Forever21 or H&M but I have bought my own fabric and made my own.
I know this is a ton so you probably don't need all of this but it's my current list! And prices could go up and down depending on stores and sales. This was fun to write so I hope I helped!
It's just a plain t-shirt and you bought it so yes you can resell it for a profit.