The light bulb gives heat, the other gives vitamins. (Sorry I forgot its name.)
I spent £160 on a starter pack. Calcium mix, food, house, bowl and more.
Heat lights are generally not good for leopard geckos. Leopard geckos are adapted to using belly heat to properly digest their food, not overhead heat. They are nocturnal, so they don't bask. Those UV lights (the tube light) have been known to cause damage to a leopard gecko's sensitive eyes and can cause skin damage as well. These geckos are not meant to be exposed to very much light.
I also noticed in your other thread that you are using sand. Sand is not a good substrate for leopard geckos. Something solid like tile, slate, or paper towels is much more appropriate. Sand can cause impaction which can result in death.
Are you measuring your temperatures?
Do you have a humid hide?