Before you hit up thrift stores, make sure that turntable actually works properly - a lot of people grab records then realize the needle or cartridge is shot, which tanks the whole experience.
Once you've got that sorted, Facebook Marketplace and local buy/sell groups tend to have better deals than you'd think, plus you can inspect stuff in person and haggle a bit.
When you're digging through bins anywhere, just flip through slowly and check the vinyl itself under light for deep scratches or warping, and always ask if you can see the record out of the sleeve. The one thing people don't mention much is that damaged records aren't always a total loss - I've scored records with minor surface noise for a few bucks that sound fine once you give them a proper clean, so learning to spot what's actually unplayable versus just grimy takes a little practice.