Hmm I think it varies from person to person along with individual perception and your face doesn't have to be attractive either!
In the early 2000's I was what is 'preppy' I guess. Was in my early 20's and a slim but very pronounced hourglass (who thought she was fat and is now a size 18 hourglass ffs!!! That'll teach me...). I have a face like the back end of a bus, an overbite but masses of curly hair.
I would wear jeans and a rounded v neck jumper or blousey top tucked in or a loose wrap cardy (had a gorgeous purple crochet Topshop one) with Cain underneath, suede or velour fitted blazer worn open, heels, pedal pushers in summer, fitted or tie back short sleeved shirt/blouse with it or mock wrap waist stripe tops, A line cord skirts with cashmere type v neck jumpers etc.
I walked tall due to a combination of heels and Pilates.
Friends always thought I looked 'expensive' and high maintenance but it took me seconds to get dressed and I'd just chuck things on,leave my hair natural and spend five minutes on my awful face
. They always thought my clothes cost a fortune and I was often asked if they were designer but they were ALWAYS cheap high street (aside from evening dresses!)
On the other side, I often got called Barbie and had some people assuming I was a bimbo!
So I think individual perception of others is a big thing. What one sees as looking 'expensive' another sees as cheap, weird or tacky (or even trashy). I often see things people say are expensive or classy looking and I think it looks like cheap market tat that only a wench would wear 
On the other side, I think how you carry yourself makes a difference. If you walk tall then you do look better. If you slouch (like I do now!), don't dress for your figure or wear things the wrong size you look worse and less put together.
I look a total mess now, which probably suits my face more (!) And find that the harder I try to look better or look more relaxed (something I always wanted) the more idiotic I look