Buy used, ideally at a local thrift shop or consignment store. There are used clothing apps like ThredUp and Poshmark if you’re looking for something specific, but keep in mind they’ll likely ship in plastic so use sparingly.
Opt for natural fibers such as cotton, hemp, and linen. Synthetic fabrics include polyester, rayon, nylon, acrylic, spandex, etc. If you have clothes made of synthetic fibers (most of us do), wash them in a GuppyFriend bag so the microplastics don’t enter rivers and oceans.
Find recycling programs at end of life. Some stores offer shoe and clothing recycling where the textiles and rubbers get repurposed.