I think you should just weigh the amount of bud you smoke a day. Say 1 g and you want to harvest twice a year so your not constantly growing. 365gs a year - 168 gs every six months. 168 / 28 = 6oz. Considering you have never grown before that may seem like a big figure but if you put the time in and read a lot of threads and maybe a book or two that could be easily achiveable. AND if you can use all the best kit such as high pressure sodium lights and good quality ferts that figure wouldnt be hard to reach at all. Id say 12 plants would grow you minimum 6ozs. Anything more, share with friends, keep it in a jar, feed it to the birds ! Obviously all these figures are irrelevant to you but you get the ideas ? Im ranting a bit now but hope this helps somewhat ! Charbud§