Two gallons sounds pretty small. But then I have never grown autos, so it might be plenty. I would go to a nursery and ask to buy used pots. Lots of times they will give them to you. It will be plastic pots, but they work alright. Or if you see landscapers doing a job, ask them for pots. The ones young fruit trees come in are about 2-3 gallons, and would work good for you.
I grow in the ground, but I have put more than one plant per hole. When you do, it is important to tie them down so they all get an equal chance at the sun. But again, I have never grown autos, so the short veg might not be ideal for multiple plants per pot.