What is the best style of clothing for an average frame and a rounder waist
Sounds like you have an apple (or 'o') shape. Basically, you gain weight in your midsection, but don't in your arms and legs. The secret with your shape is to create a waist. Steer clear of shorter jackets - great longer leaner lines with longer shirts, layers and so on. Also, try belting things - trench styles would be great for you.
Hope this helps!