Goldfish are pretty awesome. I've got three in a 55 gal tank and even then I'm looking to upgrade to a 75 or 90 gal.
A 10 gal actually isn't a great first tropical tank. I just use them for bettas. A 29 gal or 36 gal is a great first tropical tank. The larger the volume of water, the more stable the parameters are.
Happy to help :)