Alright, since it's your first cruise, definitely check out the Teen Cruising Handbook that's stickied.
Also here's what you would usually bring for a week in warm weather:
Enough shirts to last a week
Enough club-wear to last a week
3 or 4 jeans
Bathing suits
Sneakers
Flip-flops
2 sets of formal wear (dresses, suits, shoes, whatever you wear that you consider upscale formal)
A hoodie (it does get cold on occasion)
The basics -
Underwear, toothbrushes, toothpaste
Shampoo, body wash (only if you prefer certain brands; the line usually provides these in similar fashion to a hotel)
Deodorant
Hair products
Perfume
May have left some things out, but you get the general gist of things