I’m only aware of one buff:
Pre buff Gobbler: deal damage, then eat minions
Buffed Gobbler: eat all minions, then deal damage
The effect is that he now heals his allies for more since he eats all available minions, and then he deals more effective damage, since there is no remaining minion shield for the damage component of his special. This suggestion was bandied about the forum as a logical tweak to his special before it was actually implemented.
Here’s a reference thread - it looks like I noticed it on January 15th of this year, so before you obtained them.