It all depends on what equipment and substrate you are you using, for example do you know what kind of light you have? There are plants you can grows with little light all the way up to ones that need A-Z requirements but if we know you’re set up we can recommend some stuff.
Good, lightings ultra important. For substrate you might want to think about getting fluval or something comparable. As far as what plants if you don’t wanna get into a CO2 system crypticorions (prob not the right spelling) are awesome I’ve always had them in my tanks as well as Anubis, Java ferns some mosses, I would stay away from carpeting plants though unless you plan to use a CO2 system but think about route tabs they’re fairly cheap and cover a decent area .They would be in a Marina LED 20 gallon, so the light there, but I do also have a grow light for my other plants that could go near the tank if need be. Substrate will be small pebbles most likely.