Hello!
The way I got started was by buying things at cheaper stores, like Old Navy. Then I went on to midpriced stores that often have good sales, like Banana Republic and Gap, and I would wait for a sale to buy what I wanted (it was usually still available, since the sales are frequent). I just bought whatever appealed to me, even if it was something that I'd never worn before. I did a lot of online shopping, which helped me develop my style simply because I was viewing a lot of different kinds of clothing and could see what I was attracted to. (In your case, you could browse online but not order anything if you want to buy secondhand.)
I wasn't able to go to thrift stores, because I have a hard-to-find size that is not normally available in such stores, but in hindsight I am actually glad that that option was out of the equation for me. The problem with thrift stores is that they're often full of outdated things, and because there is less to pick from, sometimes you pick only what's the best of what's there rather than what you would really want if you had a better selection. Perhaps a better alternative, if it's available, would be a consignment store, because the stuff there is usually more up-to-date.
Of course, the nice thing about thrift stores is it costs very little to try out a new silhouette; however, the danger is that since there aren't different sizes of a particular item of clothing available, you might buy a size that doesn't quite fit right and then conclude that you don't like the silhouette instead of realizing that it was a fit issue.
