Gerbils are not much on climbing. They live in underground tunnels and burrows. You will need bedding for your gerbils to dig, tunnel and burrow into. With several items on market again stating “for small animals” not all of them are actually safe for small animals or gerbils.
Paper based bedding should be free of chemicals (especially baking soda, which is a poison to rodents), free of dyes and dust. Paper bedding is great for those who have reactions to wood shavings. Paper bedding is easily found in Pet stores and online.
The safest type of Wood for gerbils is Aspen Shavings or Shredded Aspen. Gerbils should never be kept on Pine or Cedar shavings. These two woods have oils that cause respiratory issues. Stay away from any package that does not list the type of wood. Some gerbils can have reactions to Aspen, this will be displayed by a red runny nose. If you or one of your gerbils have a reaction to Aspen you will need to remove it, clean the tank and find a different type of bedding.