you need to increase your budget by like 1000%.
1/2lb per plant? thats a really REALLY high goal, bare minimum wattage id use would be 1x 1000w over every 4 plants, also youll want them to be atleast (ATLEAST) 2.5 - 3 ft before starting to flower them if you wanna come close to 8 zips off each one.
my advice to you, buy 4 1k lights, get 2 4x8 tents, and put 2 1k lights in each one, in one tent run MH bulbs and use it for veg, in the other run HPS bulbs and use it for flower.
get a 9wk strain, this way youll veg for 9 weeks and flower for 9 weeks and keep rotating between the tents. once you get it dialed it you could POTENTIALLY be pulling 4lbs every 9 weeks (alternating between tents) but this will take you many many MANY months of learning... for the first few harvest youll probably be lucky to get half of that.
Im at work right now (at an indoor gardening store, its slow today) and i just totaled up everything you would need to run 2 4x8 tents (w/o co2) and it came to just under $3000, if you shop ebay you could probably do it for closer to $2000.
this is way WAYYYY more work than you think its going to be. I run 2 600w flower rooms, a veg room and a seperate 300w LED experiment and I easily spend atleast 90minutes a day tending to plants/flowers/clones, then theres that one day a week where im hunched over in tents for 2-3 hours