they might all servie if you can get the angelfish,tetras, and the danios to a bigger tank(30 gallon prepably and get 4 more tetras and 4 more zebra danios) and add 5 cherry barbs and 2 more corys to the tank you have now when you get a bigger tank for the angels if you can aford it or you may have to take the angels, danios and tetras to the store :-[ sorry that some sales person took advantage of a new hobbiest :'(
I know how you feel...exact same situation...my Otos needed a bigger, planted tank, so having no money whatsoever I asked for it for my bday and got it. Could you do that, ask for a bigger tank for your bday or Christmas? I also volunteered to do chores around the house for money like I do in the summertime. Oh yeah, and I have a job walking the neighbor's dog. I'm sure you'll find a way to make it work.
That sales said that they will be ok in groups of two so, I guss he was Just tying to sell me stuff