Buy basics (underwear, undershirts, bras, pantyhose/tights, socks, leggings, etc.) on sale or at discount or outlet stores.  Since these are items that are worn year-round, and sizes tend not to fluctuate as much, stock up when you find something you like for a good price.  With coupons and clearance racks, you should be able to get these items for at least 50% off.