Forget about jeans and t-shirts and Converse, those are not something you should wear on a dance.
A nice, fresh and young dress that's not too short nor too long will make the difference. A dress is the miraculous garment; it hides everything you might want to hide and show off the best of the female body.
If you like orange, I'm sure you'll find plenty of dresses that colour in the mall. If not, any other scolour will be okay (except black, it's not a funeral baby!), as long as you like it.
Remember, the perfect dress shpe for you depends on your body type though I always recomend the imperium cut. (the one that's tighter under the breasts and them flares down in an A-cut).
Here are some suggestions that I find casual and young:
And yes, you can wear a jacket, as long as it somehow matches your outfit, a denim jacket would be fine with any colour and would add an informal and playful tone. You can always carry a purse or a small bag...
myself as a fashionadviser