Beta will be what you would want to get or molly's....Please don't put the fish in a fish bowl, put them in a mall ten gallon with a running filter. A bowl is like living in your own waste and its harder for the fish to breathe.
none,
all fish have to have a "clean" tank at all times
now I am not talking aboout sparkly water but you have to know many things like is the ammonia too high
the only fish able to live in a bowl is a betta
no goldfish