Goldfish are dirty fish, can be really beautiful but poo a lot
. I would suggest about 4/5 goldfish and one loach too keep the glass clean. A really good pump is essential...
Goldfish dont have too look like you are thinking,
Bristol shubinkins are really beautiful goldfish, a good one will have a blue body and red and white patch's(getting close to marine fish colours)
You can get some nice yellow goldfish, or a chocolate coloured oranda, a black Moor, or a real post box red goldfish.
Mixing other types of fish in cold water is sometimes a bit tricky, but goldfish can be really nice colours and shapes and are almost indestructable.
Barlows aquatics in accy are good, but see if you can talk to Giles as he is very informed. Pat Prices place on haslingden ind est is a good place to get quality fish, and good advice if you get the right person, many good breaders sell to Pat Prices.
I am a member of the British Goldfish keepers Society (Sad puppy) and to go to one of there shows is an eye opener, fantastic fish, and you get to buy some top breaders fish
Dont believe everthing someone in 1 shop tells ya, ask a few.
If I can find any usefull links I will post them....