Welcome to AA where all your dreams come true! : D
Don't make the mistake of not cycling your tank before you get your fish. If you're not sure what that is, then have no fear! There are lots of people here that will help you!
basically it's just building a large enough bacterial colony to allow fish to live. The bigger the tank the loner to cycle (it can even tank a month of cycling before even adding fish!)
If you're new to this hobby is definitely crucial that your purchase the API Freshwater test kits.
Since you said you don't even have an aquarium yet, then a saltwater tank is out of the question as those take older tanks.
Do you have any idea what kind of fish you want? : D