first off how big do is your tank, if you want goldfish the rule for them is 1 fish per 10 gallon so if you have 5 gallon it to small but if 10 gallon only 1 goldfish remember goldfish are messy so they do a lot of waste.
types of goldfish#
black morr
comet
ryunkin
fantail
lion head
you can get
gold barb
fathead minnow
ticto barb
if you don't no any just look em up hope i helped.