oh man leopard geckos are the best <3 I love leos. My first reptile is a leopard gecko. I got her back in July and she's just so incredible and beautiful.
I use paper towel for substrate. Leopard geckos----especially young ones----poop a lot. Slate tiles are supposed to be pretty awesome though!
My gecko's warm side is 89-92F. The cool side is just room temp (usually around 70F).
Crickets and mealworms are her staples, but she also enjoys dubia. She does not like calciworms very much, but I usually sneak her a few for variety's sake. I think she just likes it when insects crunch. My gecko is (probably) 7 months old and a chunky little gal at 43g. I just feed her however much she eats in 15 minutes every day. That's usually 15-20 tiny crickets (1/4 inch), plus mealworms (I usually reserve the dubia for my beardie since he's a picky eater). Like bearded dragons, it's best to feed them only insects that are smaller than the space between their eyes.
Anything can be used for hides. In my experience, leos aren't really picky. I've used yogurt containers, cups, and toilet paper tubes. The important thing is to have at least 3 hides: one warm hide, one humid hide, and one cool hide. If you're keeping multiple geckos, add more hides. Female geckos usually aren't territorial, but why risk it?
For the humid hide, I just use an empty yogurt container with a hole cut into it. It's lined with moist moss to help with shedding and placed in the middle of the tank between the warm and cool sides.
I don't use extra lighting. Leopard geckos are nocturnal, so extra light would just irritate them. Some morphs are especially sensitive to light (albinos and enigmas are notoriously sensitive). My gecko (a bell albino) doesn't even come out until after sundown.
For heat, use an under-the-tank heater. Leopard geckos aren't a basking species, so an overhead light won't do anything for them. They need belly heat to digest their food properly. They also don't need
UVB light. In fact, it can blind them. The important thing about using an under-the-tank heater is to get a thermostat with a temperature probe. I use a Hydrofarm one. The thermostat will automatically turn your UTH on/off depending. Mine is set to turn on if the temperature drops below 87F and turn off if it gets to 92F. It's such an invaluable tool.
There are also rheostats, but those are more complicated. Cheaper, but less effective.
Co-habitating leopard geckos can be tricky. Males are often pretty aggressive towards each other (although I have heard of a few cases in which males raised from the same clutch and never exposed to a female get along). Females are usually tolerant of each other. Just watch for aggressive signs. If you see two geckos vibrate their tails and start biting at each other, you've got two males and need to separate them immediately.
Another issue with keeping leos together is making sure they are all eating enough. This is pretty easily solved by just having a separate feeding bin. I actually recommend having a separate feeding bin anyway, since it's easier to keep track of who is eating what. Plus, no worries about escaped crickets in their home tank since crickets will bite sleeping geckos and potentially cause infections.