Stressy, as an alternative to buying a new tank setup paying full retail at your LFS, be sure you also look into getting a used tank through Craigslist/local want ads or any fish clubs in your area... just in case cost is a factor. Figure out how much space you have available for the new tank and exactly how many goldfish you're going to want. Then to plan this out, estimate a
minimum of 15 gallons per goldfish for fancies and 20 gallons per goldfish for pond varieties. For the amount of money you would pay for the tank alone in a store, you could probably get a larger one that's fully equipped with all the supplies and accessories you need for a lot less. Tank size is your most important consideration right away... and whatever you find will most likely still need a big upgrade in filtration. To estimate that for a goldfish setup, figure out how many total gallons of water the tank will hold and get filters that are rated at 4 times that number of gallons filtered per hour.
For anything else you'd like to ask or discuss about setups, stocking, or basic care and feed... you might as well start a new thread for this in our main coldwater forum.
I am so happy your fish is responding well so far. We really are here to help, so whatever else we can do, just let us know.