50 plants is quite a big number. I assume this would be considered a "commercial grow". Alot of the pro's swear by 1000 watt hps bulbs (high pressure sodium) with hoods and ballasts. Ive heard each 1000 watt bulb can cover an area of about 5x5 feet approx. Then we have to get into the talk like, growing from seed or clone? soil or hydro? How long did you want to veg? if growing in soil, which is much simpler for new growers your going to have to determine pot size. Your going to have to get some specifactions, little more detail, the questions still pretty vague.