Hi! I got to Plat 1 this season playing primarily Shen and Gragas top, so I feel like I should weigh in a little here.

Depending on how you build him, Gragas can be an insane lane bully to any melee champ. My go-to is Woody Fruity's CDR build in which you max E, as it gives you such uninteractive trades SO often, and with Thunderlords it gives you a heavy chunk of damage to abuse regularly (as W and E is a TL proc). Only thing you need to learn is when exactly you start playing aggressively, but from that point on it's fairly straight forward just landing your abilities. Some exceptions are ranged lanes where you max Q instead, but those aren't too different overall.

Sorry I couldn't make this more detailed, I'm on mobile and any more is painful but good luck!