• You need to determine a budget.
• Then you can decide what kind of lights to use. (CFL's, HPS, MH, etc)
• Then drop that idea about the tomato plant. Why would you give your baby marijuana plant dirt that's already been sucked of its nutes by a dumb tomato plant?
• Get dirt bro.
Once you do that, you can start constructing. Good materials to grab if you just want to rig the structure are duct tape and cardboard boxes. Read around the forums and take ideas from experienced growers because chances are they wont give you false information.
Read read read. That's what we do.