with cannabis there really isnt any such thing as a container too big. i think a 2 gallon container in any system would make a plant root bound by the time its ready to flower. i would only use something that small for clones, seedlings, or early vegging. what kind of set up do u have. i would sugest at least a 5 gallon container for any system. some set ups promote more root growth than others though. if your using soil the size of your pot will be a limiting factor so bigger is better