What do you do against gragas in top?

Just got wrecked again...i am in plat and have a 65% win rate this split..but This feels like the hardest matchup of them all to me...thankfully very few people play him, but that also means that those people are all good at him. I am really just st a lost at how to build and play against it. His cool downs are so low that it feels impossible to punish, his slow and belly bump counter super hard. He's not worh banning since he's is so low playrate..what to do bear people?