If this is the first time you've kept Crystals, you probably should go with a different tank or go with some sort of Neo shrimp. Unless you're experienced, parameters can get outta whack easily in such a small container of water.
It's too short for most Java Ferns. You'll have to stick to Anubias, Crypts and mosses, most likely. At least if you want them to fit in your tank.
Crystal Shrimp require water with specific parameters. I.E., most are unable to use tap water and require RO/DI remineralized water with a pH of 6-6.5, KH of 0-1, GH of 5-6.
You'll likely need a substrate that buffers, so sand won't necessarily cut it.