Ok, here is my 2 cents worth. I learned my lesson well with putting down a gecko due to impaction from care at petco.
I would stay away from that stuff that you want to use. Bad.
Now here is what I do.
If you have a young gecko, paper towels. Its the easiest and best thing to use for the young ones.
Now for the larger adults 35-40 grams and up, I use sand.
People freak out on this and it is a hot topic but there is nothing wrong with sand as substrate for adults. They like to dig and move the stuff around and it gives them a variety things for them to move around on. If you dampen it, it becomes hard as well. So you are safe there on that. If you do a mixture of slate tiles and sand, half the tank with that. you should be fine as well. Been keeping geckos for years on this stuff and I have no problems. I personally got a bad gecko from petco and had to put her down due to her not eating from impaction. It does happen, but if you are careful and do not keep little ones on it, you should be fine. Young geckos are clumsy and will eat the sand going after a cricket.
So a good style cage?
I like slate with sand 50/50 with rocks or grape vine for them to climb on. And I like to give them lots of hides.