A single glider that does not get the attention it needs can actually die from loneliness. If you cannot spend this much time with your glider, then you should get 2. The litter should be made of an absorbent material. Avoid Cedar and Pine shavings. I personally prefer either corn cob or aspen shavings.
Some people also use alfalfa pellets for rabbits.
I change the litter in my cages daily. This keeps the odors down and prevents outbreaks of fruit flies and other problems. These should be kept up off the floor of the cage to prevent contamination from urine and feces. A fourth dish may be used for the weekly leadbeaters mix. Also in the cage there should be a water bottle or 2.