The best type of substrate is either newspaper or paper towels. They may not look realistic but it is safer for your gecko.
For hiding spaces i use little butter tubs or tupper ware dishes with a hole in the side or top.There should be hides on the warm/hot side and the cool side. You can also use paper towel or tiolet paper rolls. You should make some of your tupperware or butter tubs into humid hides,to aid in shedding.
You can keep one leopard gecko in a ten gallon tank. But some say bigger is always better.
They dont need to be kept in pairs.
Reptile
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4.7.2 leopard geckos (super hypo tangs, blizzards,albinos)
1.0.2 crested geckos (lite cream fire, buckskin, tiger)
1.2 golden geckos
1.1 texas collared lizards
1.1 veiled chameleons
1.0 Bearded dragon