So Cayo has come a long way, at least for a hollow. Where he starts out in Red Rover is far from where he winds up in Hokey Pokey. He's found a kind of consciousness amidst his hunger, enough to realize that staying above it makes him 'more'. That said, he does recognize the power that's in his hunger. He isn't above letting himself dive into the feral tendencies of a base hollow. Even when he does, he enjoys the feeling of it. He's able to speak more fluently and recognize mistakes he's made, like picking a fight with Levi. There really isn't a whole lot else to say about it, this is his first arc after all.
Cayo is going to continue to grow in the sense of developing more of a personality and consciousness above his hunger. Eventually he'll evolve into a gillian and have to deal with the flood of new voices inside himself, while still trying to maintain control. There will be more on that in his next milestone though.