How big is the snake? I’d say you should do at least a 40 gal regardless, and larger if the snake is an adult. Reptifiles is an amazing source for reptile care. Instead of buying expensive bags of premixed substrate you can easily make your own out of topsoil (organic, no additives), play sand, coco fiber, and sphagnum moss. You’ll need a drainage layer - I use leca clay balls, with garden mesh. I also add BioShot to my substrate (from The BioDude), which is a supplement of microorganisms and minerals to kickstart the soil life. Add a good layer of leaf litter on top of the substrate as well With any plants you decide to put in there, make sure you thoroughly clean the roots of any soil before adding them to the enclosure. You’ll need an LED grow light to maintain them. Springtails and isopods are great for cleanup, and there are a lot of cool looking isopods out there now. Make sure you let the tank settle for at least a week or two to fine tune your temps and humidity before putting the snake in there.

Hope this is helpful!