How big is the tank? Dwarf puffers in my opinion are fairly easy to care for provided that you have the right food for them. They'll eat brine shrimp, bloodworms, and probably black worms. Daphnia are also accepted. I've never had luck getting them to eat frozen food but I think it can be done. They will eat crustaceans like ghost shrimp and small fish. They are fin nippers but I've had some that were actually pretty nice in a nano community tank with peacock gobies and a scarlet badis. They do need snails to eat to keep their beaks from getting too long. Tankmate wise, I would advise an otocinclus once the tank is a few months old. Pygmy corydoras could work but any other fish would be at risk of being attacked.
Rule number one: Always research a fish before you buy it.
Rule number two: Always cycle your tank.