Dressing beautifully isn't about the clothes you wear or the face and body that you have. It's about being secure in your identity, about being confident and accepting of all the things you are (and are not). This self-awareness combined with self-confidence is then reflected in your attitude towards fashion.
Example, a woman wearing a white t-shirt and a pair of jeans. She can leave the house thinking, "Oh gosh I look so plain and boring", "My shirt makes me look fat", or worse "I'm wearing this so I don't get any attention because I'm not worthy of any attention". She'd be hunched down and timid when dealing with people, and others won't really see her outfit beyond how she sees it herself.
But then she can also see it differently. "I'm wearing this because it's classic and fresh", "My jeans make my butt and legs look nice", or "I'm making a statement that you don't have to dress to the nines to look stylish". She feels great about herself, knows what works for her, and doesn't care what other people have to say about it. That's the essence of style, I think, and it's something that will keep her back straight and her head up.
Watching TV and reading magazines fooled me into thinking that great style means glamorous, unique clothes, shoes, and bags. Well, these objects can play a role in it, but they are not a requirement. Fashion is what's new and relevant at the moment - it's an easy feat. Go inside a store with ten grand (more or less, depending) and come out with a full fashionable outfit. No sweat!
Style is how you pick your clothes with care and thought, and how you wear them with confidence. This will sound incredibly cheesy, okay, but style is a journey of self-discovery. You are not "born" with it, it's a honed skill. There is no wrong or right way to go about it and I suspect the journey doesn't really end. It's an essay of your life, your identity, and your inspirations.
The next time you go out, don't feel bad because you don't have better clothes. Own what you're putting over your skin and I promise, you'll look 100% more amazing.