What can i add to my tank?

i have a 15 gallon with currently 5 guppies, 1 neon, 1 glofish and 1 apple snail. i have a pregnant female guppy in there right now but it doesnt look like shes gunna have a lot of babies since its her first time. i was thinking a couple more neons and glofish and maybe some cory cats or ghost shrimp! what would be a good idea? thanks and please dont make me feel bad, i am new to fish so i am just learning. thanks!