Oh, wow, um, I would say return the puffer, the dojo, the dragon fish, and one pleco.
The puffer will get too large and to my knowledge should be kept alone. It is not a beginner fish for sure.
The dojo loach can get up to one foot long.
The dragon fish also gets too large (two feet).
The plecos (I'm assuming they are common plecos) can also reach over one foot.
Remember, before you buy a fish, research if it is compatible with your tank and other fish and check on how to care for it.
If you can't return them to where you got them, try Petco or Petsmart. They usually take fish (but for free).
Edit: The clown knife fish can reach 40". That is way too big for your tank.