Well, in part it depends on what you are doing with them - display or breeding rack?
For us it is display, your milage my vary:
These are tree critters, so you want tall not wide, we have a 10gallon aquarium with a 10 gallon mesh cage top, making it 20 gallon high. Again they are tree dwelling, so lots of leaves or vines or stuff to climb and hide on. If I can say one thing I always comment on is that people don't tend to put enough leafy things in their enclosures. For example, we have 2 leaf vines, a bushy tree, a plastic hide, and a hardwood ladder in addition to food and water bowls and temps/hums stuff.
As for light, again, tree critters, not a ton of light is filtered in from the high branches if you think about it. A very low wattage bulb to give a day night cycle would be all I would suggest. In fact, our crested doesn't have her own light source, her enclosure is next to our leo's which has bright light and she gets nicely filtered light that way.... obviously, that only works for us, but it works... I would guess even a nightlight on a timer would work if you've got her in the basement.
My favorite care sheet for any information can be found here, my care differs slightly due to my personal experiences, but it is a very good one none the less:
http://crestedgecko.com/cg_care.htm
They even show pictures of what a baby rack system for breeding looks like and a better adult system of leafy goodness, if you scroll to the bottom.
Good luck, ask all the questions you wish.
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0.1 Albino Leo Gecko
0.1 Crested Gecko
1.0 Dear Boyfriend
Departed: Harvey and Spock
Sorry had to.