You only allowed the water temperature to be similar. You did not let the fish to get used to the water hardness, PH, etc.
Make sure follow the true acclimate instruction. To slowly replace the water in the plastic bag with the water from the fish tank every 15 minutes or so, until all of the water in the plastic bag is from the fish tank. Add no more than 25% each time.
When you dump the water from the plastic bag, throw it away. Do not dump the water into the fish tank as the water from fish stores might have parasites and diseases.
For a 10-gallon fish tank, you can get any small tropical fish. I personally like small sized schooling fish such as Tetra. Make sure get a group of minimum 6 if you go for schooling fish. They do better in larger groups.
