If you plan on having 3 foot plants I would suggest 1 plant per container so they dont fight over soil. There is a couple of options you could do with lights, metal halide(usually for vegging) or hps(High pressure sodium usually for flowering) lights cost alot but work excellent they usually cost around 200-400$ full system but they do put out some heat so you would need ventilation, or go with cfls 6500k for vegging which is a cool white(blue color) and 2700k warm light(red color) for flowering. With compact fluorescent lights are great almost no heat expelled, can be 1-2" away from the plant and no venting needed unlike the HID lights. If you on a budget which most people are I would suggest the cfls get the 20-32 watters work really good and I would say atleast 4 per plant so you can evenly distribute the light around the plant so it doesnt grow more on one side compared to the others or you could rotated the plant with less lights. Go with the cfls learn how the plants act and what they like then upgrade to a more powerful light which would increase your yields greatly compared to cfls. Hope this helps happy growin.
