The runes are pretty simple: Ability Power Quint, Magic Pen Marks, Armor Seals, BUT... I'm not playing with magic resist runes. Why? I feel that you don't need the extra Magic Recist. You start with 30 MR but you only start with ~16 armor, which is poor. And as you know Gragas is a melee and you might get attack while you're trying to last hit (if you're going against a ranged hero).

+ It might save your life from ganks (the extra armor).

The items are pretty simple as it can be. But we got the Kage's Lucky Pick which will give you that gold advantage over your enemy, but you still get that AP you need.

The order of the Abyssal Scepter and the Deathcap is not important, you can either get the Abyssal first or the Deathcap first. But my tip too you is that if you're behind (kills, creep kills, towers etc.) you might wanna get the Abyssal Scepter just because you will need the MR to sustain from their advantage. Then after that you build Deathcap.

The Skill Sequence maybe will be seen a little odd because I choose to max Body Slam before Drunken Rage. I do that because I like the All In Damage, where you just rip your enemy with so much damage.

The farming is pretty simple, you lasthit the Melee Minions with your regular attack and then you just throw a Barrel Roll on the Caster Minions.

Everytime you throw out a Barrel Roll to farm or just to Harass you enemy, always use Drunken Rage afterwards, to get that mana back.