if you want to go cheap, you can get away with 1 42 watt Compact Floro per plant and have them all in the same area so they can share the light bouncing around. 1 above each of the tops, they run about 8 bucks a bulb at 42 watts. be creative, but if you got the money you can always get a High Pressure Sodium. a 400watt would do ok for 7 smaller plants.

p.s.
forgot to say, the more cfl's the better, but if your on a tight budget you can get away with 1x per plant and get good results, heck you might even get away with a lower watt but not reccomended, get as many as you can afford, or get the HID lights!