i dont know where you live or your current living situation but if i had 28 plants that needed pots and was looking for the cheapest method available id look into visiting the local hydroponics store (or order online) some grow bags! i wouldnt get anything less then a 3 gallon bag or your going to run into root bound issues and it could effect the quality and quantity of your yeilds.

Grow bags are cheap! last time i ordered some i think it was around 50 cents a grow bag maybe even less!

Another cheap option would be to drive around construction sites where painters have already come and gone and you might be able to score a few old empty 5 gallon paint buckets (Make sure to wash them out RLY good and drill some drainage holes in the bottom)

*a cheap container to veg plants in are tall keg cups (plastic red or blue cups that college kids drink beer outa) you can usuly get away with keg cups for a few weeks worth of veg. Remember, stabilizer roots grow down about as far as the plant is tall and roots grow out about as far as your canopy does. If you ignore this fact for too long your plant will become root bound and will not have the plant vigor and growth that it should.

*also when you transplant, if you notice on the side and bottom or your root ball are substantially built up with strong white roots dont be afraid the rough up the roots ball (literally take a razor and cut the root ball a bunch of times if the plant is root bound) this promotes NEW root development (because the root to shoot disturbance)