I started with guppies and I think that is a really good option. They are pretty good starter fish. There are different colors of them so almost all of them look different from each other. That means you get a good variety. Guppies are also pretty hardy so they probably won't just die off. They mate very fast also so you can always have guppies in your tank
By the way guppies are freshwater fish. You don't have to have a bottom feeder, just don't over feed your fish too much
You also have to make sure you cycle your tank first which you can look up online.
You could also try a betta. I haven't had one but I'm thinking about getting one. Bettas have long fins and are really pretty and bright. They are aslo freshwater fish. They are usually aggressive to other fish, especially there own kind so don't get more than one. Betttas are also pretty hardy fish. They can live with some other fish but not a lot but I think just one betta in your tank with some plants would look beatiful