eh in my opinion....
giant danio= 55g with a school of 6
jack dempsey could live there with them.
the pleco if its a common or sailfin will probably get 18inches on average....maybe a 125g min.
the dragon goby i know nothing about in terms of tank size...but i know for a fact it is brackish and i have heard they need live foods and refuse pellets and flakes.
i say get a pair of rams....a school of 8 smaller tetras...and a bristlenose and call it a night