No lighting is needed at all......you could raise a healthy leopard gecko in complete darkness and it would physically be healthy.
Although psychologically, you need to provide some sort of light to establish a photo-period and circadian rhythm(12 hours of daylight). A simple room light would be fine, but you said your basement doesn't get much light......so you might need to get a simple overhead light (doesn't have to be UVB).
But know this : UVB is beneficial to all living things, so it isn't a bad idea. But leopard geckos DO NOT require UVB for proper bone growth like some other lizards.
A simple undertank heater that "covers" about 1/3 of the tank's bottom surface is recommended. This way you don't have to switch with two light (red for night and bright light for day) to provide a heat source 24/7..............the undertank heater can run all day every day.
For the best information, I highly suggest picking up a copy of Ron Tremper's book "The Herpetoculture of Leopard Geckos"........it's 250 pages of extremely detailed husbandry information and can be bought on Amazon.com for around $20
EDIT: Why is everyone suggesting red night bulbs? In my opinion it's too much of a hassle to have two different light sources/bulbs......not to mention a leopard gecko won't usually bask under extreme light. That's why an under-tank mat/pad is better, because the gecko can benefit from the heat while curled up in a hiding box/cave.
Just let the Under-tank heater run 24/7 and you don't have to worry about "red bulbs" or "basking lights".
And to the above poster that said UVB was bad...........WHAT? UVB is beneficial to all reptiles, albeit not entirely vital. A UVB light would however be a waste of money seeing as how leos are nocturnal and wouldn't benefit from it to justify purchasing it.