What makes a leopard gecko happy?

I just got 2 female leopard geckos today. They appear to be healthy and get along fine. Im going to watch them closely to make sure they don't have any health problems and don't fight. I had a leopard gecko before so I know allot about taking care of them. There are in a twenty gallon and housed on paper towels for now but I plan to add slate tile instead. The lady that sold them to me said they need 2 hides per type of hide per gecko. This is highly unreasonable as i would have to have 6 hides and that just won't fit in there. At least with the hides I have now. If i get more hides do they have to be really dark inside or can they be in things like half logs. I have 4 hides in there now. 2 small 1 humid and 1 large. Should I replace the large with two small? Any help is appreciated.