Pre-drink with W before the play is visible, because Gragas is much cleaner when the damage reduction and empowered hit are already loaded instead of arriving late after contact starts
Explosive Cask is a steering wheel: throw it behind the target or after E lands so you choose whether that body ends up in your team, tower range, or off your carry, rather than just blasting someone away
Treat the first clear as buying short, ugly contact, not a river coin flip; Gragas holds up when that early damage timing lands on schedule, but he drops fast when the opening leaves him late to first component or in a real gold hole
If you are unsure, wait half a beat longer than your first instinct. The clean Gragas R is usually the one that fixes a path, not the one that starts the clip. In ganks, hold it until the target has shown where they want to leave, then throw them back through that line or back into your team after E connects. In skirmishes, use it on the body whose position changes the whole fight, which is often the diver who has already stepped too far rather than the carry you cannot cleanly reach. If your cask only creates distance and resets everyone, it was probably early.
Gragas periodically heals upon using a skill.
Gragas rolls his cask to a location, which can be activated to explode or will explode on its own after 4 seconds. The potency of the explosion increases over time. Enemies struck by the blast have their Move Speed slowed.
Gragas samples his latest brew for 1 second. After finishing, he becomes boisterous and belligerent, dealing magic damage to all nearby enemies on his next basic attack and reducing damage received.
Gragas charges to a location and collides with the first enemy unit he comes across, dealing damage to all nearby enemy units and stunning them.
Gragas hurls his cask to a location, dealing damage and knocking back enemies caught in the blast radius.