Definitely most furniture (i.e., without cushions so you avoid bed bugs). New furniture is incredibly expensive and (seems to be) lower quality. Second hand furniture can still be expensive but it’s usually heavily discounted, especially if someone is trying to get rid of it quickly.

Local thrift shops are a good option of course, but also try garage/yard sales, Craigslist, OfferUp, etc. If your area has estate sales you can find some pretty killer deals on good furniture there too.