Good to see a decent size tank for your Betta. You made a good decision on the size, as Betta fish like to swim, and their big fins mean they need room to turn around and not get their tail snagged on something.
The snail may eventually out grow the space, but they are great cleaners and very fun to watch.
The shrimp may or may not last depending on the situation with the betta. Sometimes a Betta will be the nicest tank mate with shrimp and or snails (and sometimes a fish tank mate of differnt kind not Betta) and for 6 months there is peace and harmony, and one day/week he goes on a killing spree and their is nothing left.
For the past ~13 years I have kept Betta fish. It started long ago when people felt that the fish was a decoration and kept them in a .5-1G vase with a few pebbles and a Peace lily growing out the top.
From your post and new tank, I can see you decided a fish was a cool creature to have and that the fish is VERY important and not just a decoration. Seeing that you are really loving fish keeping, being here on AA will be a big help. People here LOVE their fish, they love other peoples fish, and want the best for them. So glad you are here to learn as much as you can to be the best fish and invert keeper you can be.
Welcome to AA and water critter keeping