ON ething that I think you're going to find out is that you should have had all this thought out b4 starting the seeds.

That said, the first thing you need is soil. I would by a good name brand potting soil with time release fert. already in it. This isnt ideal but for a novice it will help you a lot. Make sure the soil has a good mix of perlite, vermiculite, and organic matter in it. It should stay in a clump when you clench it in your fist but should break apart easily when poked with a finger. If it doesn't break apart easily you will need to amend the soil with the above mentioned items.

Second thing is the lights. You have two choices imo. HID and fluorescents. Since your intended garden will be long and narrow fluorescents could be a good choice for you. If you can hang four 4' fluorescents you could do alright. HID would be my choice. The home depot here doesn't carry any remote ballast HID systems. IF you do get an HID I would definately recomend a remote ballast because of the heat build up in the small space you'll be growing in. I know Walmart used to carry fluorescent fixtures that would hold two 4' tubes for around $10 - $15 apiece. You could get two of those and then order a decent HPS system which would arrive when you are about ready to flower.

How many seeds depend on the lights you get. If you get the 4' fluorescents then you are only going to be lighting 8 square feet of your closet. In that space I would recomend 4 seeds in 4 five gallon buckets with holes drilled in the bottom. Then set those inside other 5 gallon buckets with no holes (to catch run off water). The left over space could be used for a decent oscillating fan and any other equipment. Dont forget to put up mylar, a reflective emergency blanket ( I think home depot has these if not walmart does ), or paint the walls flat white to maximize the lighting.

Plant the seeds between 1/4" and 1/2" deep.

For the seedlings keep the closet about 75 F

Hope this help a little

Good luck