Hi
The warm end needs to be kept between 88 to 90 degrees, so you will need an inexspensive temperature gauge that you will put on the inside of the warm end, about l inch up from the base.
You will also need a humid hide in the tank 24/7, I put a papertowel in it and keep it moist not soaking wet all the time. This really helps a gecko to shed when it is time.
You will need to keep a cap of straight calcium powder in a cap in the tank 24/7 that doesn't have D3 in it or anything else. You will also need to dust the crickets with calcium with D3 in it everytime before feeding the gecko. Why the cap of calcium in the tank also, that is so when the gecko needs extra calcium for there bones it can lick it as needed.
You can use the human heat pad if it keeps the warm end warm enough and it should be set on low. If it doesn't keep the righ temp., then you will need to switch to an under the tank heat source. They need that bellie warmth to be able to digest there food properly.
Sand, Calci sand and other kinds of sand is the worst thing you can use for a gecko, because there is a chance they can become impacted. They get the sand in there mouths when diving for there food. Newspapers and papertowels are the best substrate source. You could also use slate, reptile carpet or tile. If a gecko gets impacted and can't no one can get it cleared out, then a gecko can die from it.
Take Care, TLB
p.s. sorry this is so long. Feel free to ask anymore questions.