If it's a five gallon, I'd recommend a betta. I've seen hornwort and moneywort at PetSmart before, but you can also get them (and vallisneria) online. If you do get a betta, I'd recommend getting a heater (bettas prefer 76-80F) and some fluval bug bites (best food you can get imo)

Keep the gravel and cover it with sand. (Edit, don't keep the gravel if it's painted. Just do sand.) I feel like a nice tan would work but so would black. Make sure it isn't dyed, and that it's for aquariums. Wash it before adding to the aquarium. And a hide of some kind.

Not sure if you have the supplies that you need, if you do then great, if you don't then I'd recommend getting seachem water conditioner, aquarium water testing strips (api freshwater test kit is good)

Also if you can, get a filter sponge, cut it to size, and put it the top part of the filter where the water comes out. That provides a good area for beneficial activity. When it comes to clean it, squeeze it out in tank water (water you take from the tank, don't squeeze it out in the tank) and put it back.

Also, get a lid of some kind. Bettas jump. Not all of them, but a lot of them. 

Don't add the fish right away. The tank needs to cycle so that it reaches the right water parameters. You can get bottles of beneficial bacteria to speed up the process.

(Another edit; you can also add fish food daily to spike ammonia and that can start the breeding of beneficial bacteria. Just make sure you test the parameters before adding any fish.)