I'm going to the cappies! Now I need a gown... help?

If you're unfamiliar, the cappies is like the Emmys for high school. So I'm looking for an academy awards style gown for preferably under $120. I have a small waist and large hips and , so I want something that doesn't accentuate my backside. I tend to look best in earthy/mermaid tones. Please help me find a gown!