Just a few other comments, I agree with all of the above.
Some of the fish/creatures you're picking can be difficult to keep regardless of the tank age. Tangs, especially, have a hard time traveling. Powder Blues and Browns have always been ich magnets for me. Inverts like shrimp can have a very hard time if your water quality is off. Hermits and snails are almost always short-lived, so you don't know if it's their lifespan, a predator, or water conditions.
Many will disagree, but for your first fish I would start with someone less expensive and hardier. Damsels are notoriously tough, but hard to catch later if you don't want them. I've always had good luck with dwarf angels to begin. Hawkfish have also done well for me.
I would avoid exotic shrimp, starfish, and expensive fish until you start to see some success.