Nice start, even though 6 is the minimum school size in a tank that size you can have (and I recommend) a larger school.
You could easily keep 10-12 corys, I have kept that many in my 75. Would have kept more but lfs has not gotten them in.
Same for the other species, lots of options in a tank that size. Smaller fish like small tetras look great the more you get. I have 6 Australian rainbows in mine (get 3" +), well I did but I had to empty it to reseal it.