depends on the portion of the grow. for flowering, use warm white (2700 or 3000k), for vegetation and seedlings and clones use the coolest white , bright white bulbs (6500k)
Bright white = vegging and sprouting/Flowering supplimental full spectrum bulb 5500k or about you want the 40 watters
Daylight =Vegging and sprouting there 6700k for great vegative growth you want 27 watt or up
Softwhite= Flowering bulb promoting bud sites and budding.. there 2700k 23 watts or up I recommend the 30 watters
Shop light T12 2 bulb unit 5000 lumens per are 8 dollars and a great addition to any grow hang vertically for lots of coverage.. the bulbs are the same as above.. daylight for veg and coolwhite for flowering
check my sig for my link and look at the end pictures of todays grow rooma and setup