Maybe something like this This particular dress was from This Next (I saw it online, but you could look for something similar wherever you like to shop). I think I would pick a different color, maybe red or pink or lime.
Or this which is Isaac Mizrahi from Target.
Or this I saw this one on a blog, so I’m not sure where it’s from, but I’ve seen things like this in most of the regular stores that sell dresses for teens.
Or this I saw this one on ioffer.com.
Or this one also seen on ioffer.com
Or this one which I saw on watchmojo.com
Go through some magazines like 17 and cut out some pictures of dresses that you like so you can take them to the stores that you like to shop and ask the clerk to show you something similar. You might also enjoy going out to some thrift stores, they often have a nice supply of party dresses (some really cool vintage ones) that you might like, or even try David’s Bridal. Have fun!