HPS is the most important light you will need. You can grow good bud with only a HPS. HPS is the light you need for fat buds. The MH or florescent lights have a better spectrum for veg, as the HPS spectrum causes some steching. You can get a MH conversion bulb for veg.
Dont skimp on the hood, the bulb must be behind glass! For heat and to prevent a fire which would attract the attention of the cops.
If you have close access to the hydro shop a cheep magnatic ballast will do. Sometimes the ballast breaks, so if you are in the 6th weeb of budding that is a major problem. If the hydro shop is close make sure you can get quick service in an emergency, it must be same day service as your plants cant be in the dark for many days. If a hydro shop is far get an expencive magnatic ballast.
The thing is for any kind of efficent grow you need to be able to take clones. So you want to be thinking allong those lines now. Your first few grows will surly have too many males so the harvest will be a bit small. You need to get a good strain and clone it so all your bud can be killer. Cloning is hard and you should try as soon as you can.