For dresses, you want to focus on balance. You don't need a huge, poofy skirt, but something with a bit of fabric and width will allow the skirt to flow over your hips and thighs, hiding any imperfections. Be careful about length -- you don't want the hem to hit at the widest part of your leg. Something like this Calvin Klein Surplice Satin Dress, $198 at Nordstrom would be gorgeous on you.