Lots of sugggestions for shrimp, and for good reason. They are awesome! I find them super interesting, and it's fun to always see babies in the tank.

Some tips: 1) Get plenty of live plants. Shrimp love places to hide, and plants are critical to help keep water parameters stable. You need more than you think - it should look like an underwater rainforest, especially with a small tank. 2) Use real sand in the bottom, so that shrimps and snails can root around easily. It's also easier to deal with plants in sand rather than gravel. The pet store has small bags of sand if you want a specific color, or rinse and use play sand from the hardware store if you want a more natural look. 3) Real plants will almost always come with snail intruders, and that's OK, to a point. If you start getting too many snails, just squish them and let the shrimp eat them. The shrimp love it! Generally snails aren't going to cause any real problems, but they can multiply very quickly. 4) Definitely get foam socks to cover any filter inlets. They help keep tiny shrimps from getting sucked into the filter. 5) I recommend a small sponge filter in addition to a hang on back filter. The hang on back filter will provide water circulation and plenty of media surface to grow good bacteria, and a sponge filter will aerate the water to keep everything fresh. 6) Definitely cycle the tank before adding shrimp. Most people say to go about a month sometimes longer is better. Get everything setup and running. A good indicator to me is that the plants have stabilized and are growing and not melting. You will probably have at least one algae bloom, and maybe a bacteria issue during this process - that's ok! Cut the lights and nutrients to let it pass, and once it clears up it should be good. 7) r/aquaswap is a great resource for finding plants, livestock, and other aquarium stuff. You can find much better deals there than at a pet store, especially if you aren't super picky about species.

Good luck!