If you watch a show like What not to Wear on TLC they can give you "rules" for certain body types. watch carefully. Most of them for plus size girls suggest fitted high waist, neckline that shows a "decent" amount of skin (instead of INDECENT which seems to be a trade mark for the plus sized gal) and for dresses, something that comes away from the hips.
I, myself, am a Retro FIEND so I wear a lot of retro inspired dresses. It's nice, because they all fit that silhouette.
I agree with toasted that you should start collecting looks you like and identify with and then you can find the pieces that echo that look. I like stores like Torrid for younger gals. are you familiar with them?
I LOVE fashion. I love to play dress up. It's very much how I outlet my "Drama" and my art. I'd love to give you input once you've made some choices.
Good Luck! Have fun! Reinventing yourself is SO cathartic!
"The most difficult thing is the decision to act, the rest is merely tenacity. The fears are paper tigers. You can do anything you decide to do. You can act to change and control your life; and the procedure , the process is its own reward."
~ Amelia Earhart