Also look for nurseries or landscapers that sell/plant trees. You may be able to get used tree nursery pot/totes for free or low cost. These are 25 gal to really big (100-150 gal) and have a lot of drain holes making them usable for anything else. Lowes & Home Depot might have used 25 gal & 35 gal large pots for free.
Here is a link for
65 gal pot at less than $30. Do a google search for 50 gal fabric nursery bags. These are about $15.