Unfortuntely a 1 gallon is not good for many if any fish at all. Petsmart should have 10 gallon tank for around $10. If you get a good sponge filter and an airstone then you could get a lot of different small fish to put in there. A heater will also be needed for most fish except Goldfish
If I remember my numbers right, I can get a full 10 gallon setup with HOB filter, tank, heater and gravel for around $40 from Wal-mart. Although I don't recommend the AquaView filters they will work in a pinch.
If you get the 20 gallon it will work for quite a while for the Goldfish
. I would still try to take them back though and get some danios for cycling the tank. 8-12 of them in a 20 gallon should be enough to cycle it fairly well and not have a huge ammonia problem. If they won't take them back use them to cycle the tank and then get the fish you want for it and find someone who wants the goldies.
BTW, I want to commend you for coming here and getting good information to help your fish survive and turn this into a pleasureable experience that I hope will grow on you.