I am not generally lucky at yard sales, or GoodWill. I can't remember seeing the kind of pots I like at GoodWill. I guess they, too, have a gardener working for them. I have been lucky when 2 different gardening friends gave me a whole slew of terracotta pots. One gave me 6 20-inch pots, which was like Christmas morning for me. They came just at the right time, after I had rescued a whole bunch rare philodendrons and needed to pot them badly.
Another friend gave me 18 8-inch terracotta pots. That, too was very welcome. I always have my eyes open on trash day because people throw out the darnedest things. You won't catch me dumpster diving, but I have no qualms picking through curbside trash.
Keep well.
Sylvain.