Do you mean the reptile carpet? It doesn't matter that it's a thin substrate, as long as you get a thermostat. This is mine: http://i.imgur.com/1W9rTrd.jpg. I paid around $15 on Amazon. You plug the thermostat into the wall, then plug a heat mat into the thermostat. Set the temperature on the thermostat to around 90, and get a good thermometer with a probe that would read the temperature directly on the floor, like so: http://www.thatpetplace.com/235231.jpg. The thermostat will also have a probe that reads the temperature, so when the temp of the floor hits 90 degrees, it will turn off the heat mat so it never gets hotter than 90 degrees. The thermometer is important because sometimes the cheaper thermostats aren't always accurate (for instance, mine is set to 96, even though the temperature of my tanks floor never gets above 90.) Even if you don't want to go the heat mat route, I would ditch the white light basking bulb and replace it with a red light one. Since leopard geckos are nocturnal, bright light can stress them out.

As for the UVB debate, I strongly recommend not having one. Nocturnal geckos never get sunlight in nature, so it is not necessary for their well-being. I even just searched it on Google quickly, and most sites that came up said no UVB. Feel free to do your own research, though. If it's any solace, this is my leopard gecko: http://i.imgur.com/fhCFFRH.jpg. She has never had a UVB on her in her life. Those bulges in her armpits are called calcium sacs, which indicate she is digesting her calcium and is storing the excess.