In a 3x2x3 so a little box it sounds you will not need much light if you are mylar'ing or some sort of reflective inside.
I would say run a couple CFLS to drop in for some light for the popcorn stuff and keep 2-3 3ft's up top thats about 120 w on top plus any cfls you add. Low wattage will help profits, and you can increase profits by making sure to reflective the sides, flat white paint at least.