Your best bet might be to go to a makeup counter like MAC. You can bring them a picture of you in your dress -- or at least of your dress -- and tell them you're going to be in a ballroom competition and get them to help you pick things.
The colors are all going to depend on your skin tone and your dress color. Personally, I like to wear rich reds, not bright ones, but ones that are just slightly browned a bit. MAC's "Mystic" is one of my favorites, as is "O." I hate lip gloss and so don't use it. I always use blush and have never used bronzer. I do, however, use self-tanning cream on my face and any other parts of my body that will show in my dress. I use eyeshadows in neutrals that go with my skin tone -- deep pinky browns, or pinky greys, with an accent color that brings out my eye color or contrasts (but doesn't clash) with my dress.
It takes some experimentation to find the best personal look. Is there a female teacher at your studio you can ask for a bit of advice, or another student who has been doing this longer than you? I'm just suggesting that you talk to someone in person because that way they can take your skin tone, eye color, and hair color into account.