First off, welcome.
Honestly, To be fair, I think before you get into the hobby, you should do alot of research on here before you fill that tank. It's very good to get some knowledge down and set before your into the hobby. It's like going to the dealership and buying a car before you even sit in it and drive. Just because the picture looks nice, does not mean it's for you. The hobby is not hard, and you can easily pull off a tank I'm sure, but you really should read alot first. For instance, live sand is pretty much a must, and a skimmer is a must, but if you read alot on here fist, your going to see why your 15 gallon set up might be a pain for a first tank. BUT... It is possible.
100% Rodi water.
A good hang on filter.
Bio wheel or something.
A skimmer is mandatory, but for your tank, you may be able to do it without one since it's so small.
A hydor mini koralia
Live sand, caribsea is good brand, lots to pick from
Salt obviously. Personally I use esv, but would not recommend it to you. It's not a beginners salt. Look for h2ocean or something like that.
Refractometer
Test kit
Heater
Thermometer
Light fixture. Light is very important. Thing is, you should not do coral yet, but I'd get a good light. Your flor. Fixture is going to be such a boring color that your going to hate it! Presentation is going to be everything for someone new to the hobby. The color is going to matter the most. A simple flor fixture is going to be a yellow/white color. Everything will look dull...
Then, when it's running, about 20-25 pounds of live rock
Good luck...
