i transplant like this:

16oz keg cup to 5 1/2 inch square pot to 1 gal to 3 gal to 5 gal

you just wait until the roots fill the container then transplant to the next size. i use thrive alive red(b1) when i transplant. i know to transplant when i have to water everyday or every other day to keep the plant from wilting.
good luck!