A 5g tank doesn't give much swim space for a schooling fish like cherry barbs.
You could possible only handle 2-3, but really, they should be in a bigger tank with at least 6 for a school.
for a 5 gallon 3 guppies, OR 3 endlers, OR a dwarf puffer OR a betta are about all you could have.
Cherry barbs need a school and thus a larger tank. a school of 5 (recommended amount is usually 6). would be 10 inches of fish in a 5 gallon tank.
I had my school in a 10 gallon tank for a while and they did really good, then they started the get bigger and wnat to uh... well... ya, you know. So I moved them to my 20 gallon tank, they are much happier and soon I will get it planted. I would recomend a nice male betta from a cup at Wal-mart. always a good feeling when you rescue a betta.
But when you do get a bigger tank, be sure to get a school of cherry barbs, great little fish in my opinion, and the males look awsome when they want to breed!