High tech garden supply has some great prices on their HID lights.
You can get everything else from walmart.
A tub like this is $5
You can get a powerhead like this for $20
an airpump like this for $10
With some epoxy and some clear line you can make a sight gauge like this,
Don't bother with airstones.
Just stick the airline into the tub and let it bubble.
Throw the powerhead in the bottom and let it run.
You can make your own net pots.
and use lava rocks or aquarium rocks.