I've done OK with forest mulch such as is used for flower beds and around tree bases. It might work out to use cypress mulch although that is more expensive. When I've used mulch, I make sure to get a clean mulch that does not contain "greenwaste"--little bits of plastic bags and other supposedly benign human flotsam. One thing about mulch, it can be moistened without compacting or getting nasty. It's relatively easy for animals to spit out if they get some in their mouths while eating and it contains beneficial bacteria so it can be used for several months with spot cleaning if the enclosure is not overloaded with animals.
My preference is dune sand. I live in Michigan where dune sand is quarried in the western part of the state and sold as play sand. Dune sand has weathered from the grains blowing against each other. It has rounded, eroded contours instead of the jagged surfaces sometimes found in play sand, which is often quarried from underground or made from crushing quartz rock. I have never had animals suffer from sand impaction in their intestines while using dune sand. I do feed my animals by putting food in dishes to minimize the chances they will accidentally swallow substrate when eating.
Beach sand is also very well eroded, probably more than dune sand.
That said, Eve's method of using paper sounds good especially for animals in quarantine or those with special needs. Home Depot sells rolls of brown kraft paper for covering floors while painting. The paper has good stiffness and texture and ought to work nicely for a cage floor covering. If it gets a little wet it cockles into tiny ridges that might give extra traction, so lightly wetting a fresh piece before adding lizards might be useful.
