what would be a good first fish tank?

I wanna get my partner a fish tank, not as a surprise , because dumping random animals on people are horrible, me and her just want ideas, I was thinking a tank with plants with a snail (I know they can go crazy) and maybe some shrimp?, what size tank would be good for that and over all, what care would be needed, I personally plan on doing a tank like this for my 15 gallon at some point, Im new to fish keeping sorta, but ya, any ideas?