I use playsand to cap my soil based planted tanks and lots of folks use sand alone with and without plants
Good low light plants are most stem plants like naja grass, ludwigia, rotala, hygrophila, water wiateria, moneywort, anacharis...other low light plants-java fern, java moss, anubias all need to be tied to something-sags, val, swords, crypts all good low light easy care type plants and the list goes on.......
With plants you need at least 1.5wpg and 2-2.5wpg even better and can give you more choices without needing any CO2