Hey there! My name is jaxonplaysgames. I am currently Silver II right now in League of Legends. I used to like to play Gragas mid, it was one of my favorite metas. But after his changes I didn't really like Gragas anymore because they made him not a strong mid-laner. After trying him as Top and Support, I realized that he had the mechanics to become a strong jungler. (Btw this is my first build so sorry if it is not so detailed.)

These runes work very well with Gragas. The 3 AP quints, help Gragas early in the jungle and securing kills. I run 9 magic resist glyphs if their team has a bursty Ap champ or an Ap Jungler. If their team has neither consider running armor or AP glyphs there. The health and armor seals help tremendously when ganking, and clearing jungle camps. The health and magic penetration marks help Gragas in the jungle, ganks, and securing kills when the enemy team builds magic resist.

The skill sequence is pretty basic:

Max R whenever you can
Max Q first to have an easier time in the jungle
Then Max W for the extra damage on the first hit for the huge jungle monster (momma wolf, big wraith, big golem, etc.)
Finally Max E for the extra damage to the jungle monsters

Pros

Great clear times above level 3
Great ganking potential
Lots of combos for jungling

Cons

-Not Strong Very Early
-If the other team invades your blue you will have a terrible jungling experience, because you rely on blue

Make sure to get a leash for blue and then go a basic rotation by taking wolves then heading to your red. When you hit level 3 gank top. If that is successful you might get a level up. Anyway just keep clearing camps and backing to pick up that first item. When you get level 6 you want to gank bot, if they are overextended gank mid. Ult the enemy/enemies towards your team and then follow up with throwing your Q, letting it sit for 1-2 seconds then detonating it. Then either E forward while your team lays down damage, or W and hit the enemy, then E if you have time. Most likely this combo will result in a kill. Continue to use your jungle combos. Q the camp over the wall, then W, then E over the wall and hit the big monster first. Keep repeating this and ganking using your combo over and over again.

1. All In Kill Combo
Ult the enemy/enemies towards your team and then follow up with throwing your Q, letting it sit for 1-2 seconds then detonating it. Then either E forward while your team lays down damage, or W and hit the enemy, then E if you have time. Most likely this combo will result in a kill.

2. Jungle Clearing Combo
Q the camp over the wall, then W, then E over the wall and hit the big monster first.

3. Flash Trick
If you E with Gragas and flash at the same time you can get maximum distance with your E.

4. Flash E Behind
Another combo used for mostly late game in teamfights is: flash forward in front of an enemy, you can then E backwards towards your team carrying the enemy with you. Then your team can pick off this enemy.

5. Flash Ult Pick Off
Another combo used for mostly late game in teamfights is: flash forward in front of an enemy, then R that enemy back, this will fly the enemy back into your team, and fly the other enemies in the other direction. This is a great combo if you need to pick someone off.

6. Baron Steal Combo
If the other team is taking Baron Nashor, this is a combo to steal it. Place down a ward in the pit. If the other team is taking the baron, throw your Q in the pit and let it sit, then when the baron gets low, W, E in the baron pit and hit the baron with your W, then throw your ult on the baron, explode your Q, and smite the Baron all at the same time.

So as you can see from this build that Gragas Jungle destroys the other team, just think of them with no baron buffs, no dragons, and picking off people on their team to win teamfights. The rest is simple, just take turrets, inhibitors, and their Nexus. And that's all I have here from jaxonplaysgames. GG AND PEACE.