If you're going to use only one HID bulb (MH or HPS) at a time I suggest getting a conversion bulb (MH that fits in HPS ballast or vice versa) and just switch the bulbs when needed. Buying a whole seperate ballast and bulb when you're going to only be using one at a time would be a waste of money. Also, if you have a decent amount of money to get started I'd suggest making a DWC Bubbler hydro system (very easy).

Simply buy the following things:

5 Gallon Bucket. $3 or so
5inch net pot. under $1
rockwool (only thing off the top of my head for seedlight sprouting). Prolly like $3-5
a dual outlet fish air pump. $12
2 Air stones (the little attachment for the pump to make bubbles really small). $2-5
and probably nutes.

Doesn't cost too much and it would GREATLY increase you're yield and probably vegging time (not sure).

Also I would suggest making 2 as apposed to one simply because of the fact that you can get a male then have wasted all your time.

Goodluck.