When you were a kid, you probably got lots of hand-me downs. Your cousin, your siblings, older kids you knew, everyone was giving you their old clothes that they grew out of. Sometimes you got things that didn't work. (I was once gifted a blue velour sweat set. Powder blue. Oh yeah baby.) But other times you got really cool pieces that you wore for years.
I still love getting clothes from friends. (I don't just befriend people based on their taste in clothes, though. Much.) Whenever I like something someone is wearing, I just subtly drop a hint about passing it on. Nothing obvious. Just really casually, like "Hey there. That top is really awesome. Whenever you decide you don't want it just, you know, give it to me and never hope to have it back." Super subtle.
If you don't have stylish friends (you just thought of someone, didn't you?) then there is also Vestiaire Collective. It's kind of like eBay, but only for designer pieces. They're lightly used and often highly discounted. It's a great option for getting pieces you want.
Another fun thing to do is to throw a closet swapping party. Invite all your gal pals over, each bearing a few pieces (nice ones) that they're ready to pass on. You may want to specify that the clothes can't be ratty, they can't be from 1986, and they have to be freshly washed. (But, that again depends on your friends.) Serve some hors d'oevures and enjoy.