In my experience with reptiles, I am highly against heating pads and heat rocks. The high risk of thermal runaway due to thermostat failure or heating element shorts is unacceptable to me. In the case of desert species, under tank heating can be fatal. These animals tend to burrow to cool down and if the substrate is warm, they quickly succumb to overheating and dehydration.

The best alternative is to use either a metal halide type spot bulb, which provides needed UVB AND a hot spot basking area, or to use my personal favorite- the ceramic infrared heaters.

(I do not waste money of the pet shop ones, I buy them from industrial or livestock supply houses. Pet shop brands are overpriced fourth party mark ups of the exact same products with fancier packaging)

Leopard geckos do best in daytime temperatures around 80°F +/- 5°. Night time temperatures should be around anywhere from 65 to 75 °F.

A daytime basking area with an ambient temperature of 90-100°F should be provided. Keep in mind that ambient air temp is very, very different from the surface temp of the basking surface. The surface temp should be anywhere from 90-125°F!

Keep in mind they will need a cool area to hide, so provide hides as far from the basking source as possible. If your enclosure is large enough, a temperature gradient of 75° on one side easing up to 80° on the other is best. Keep the hides on the cool side and the non plastic basking surface on the hot side. An intermediate temp hide is a good idea too.