i noticed your use of "cointainers" i found that living in CA there are lots of wholesale plant farms... and they stock pile all size plastic pots .. i bought 10 one gallon 6 inch used pots for $4 thats .40 cents a pot and the larger pots are just as cheap. if all else fails you have th right idea party cups are cheap and in some cases free.. as for space you can fit for 6 inch pots in a square foot space