What kind of dress should i wear to a wedding that is in myrtle beach?

The wedding is my Boyfriends brother and his finance is very fancy. I myself don't like to wear dresses. I am a jeans and t-shirt kinda girl. She thinks his family is a bunch of hillbillies, which we are not at all. I wanna show her we aren't by wearing an awesome dress but don't know what kind of dress, or where to look. I am not one to buy one online, i like to try it on first. Another big factor is i don't want to spend a lot of money on it either...