I completely understand the budget angle... I've been trying to do everything as low cost as possible.
Assuming you already have a hood that is big enough to fit CFLs under and has lights that you want to upgrade in it. I don't think you will beat DIY retrofitting of the hood for price if you want to increase lighting to 2wpg or more.
Costs:
$2.50 per light socket
$3 per CFL
$4 white Spray Paint
guessing $1 Wire connectors (if you don't have them- I did as a student you probably don't)
If you do what I did- 6x20watt 6500Kelvin CFLs: (6*2.50) + (6*3) + 4 + 1 = $38
Oh, and if you don't have machine screws and bolts to attach to top of hood add another buck or two: $40.
I really don't think there is a less expensive option unless you luck out someone selling a hood with lights on e-bay or Craigslist for less.
Wiring is VERY simple- just connect the wires coming into the existing hood to your light sockets- although if you've never done anything like it before you may want a friend who is handy to help. Loose wires, electricity and water is a potential recipe for disaster if you're not carefull!
If you don't already have a low powered light hood to refit it's going to cost you more buying a light source.
If you just have fish and no plants- You don't really need any light. Even if you have low light- ambient room light- some plants like Java Ferns would still grow.
There are options for the budgetry minded. (is budgetry a word?)
