I've been playing a lot of 
recently, and I have had some games where I would do good, and some games where I would do terrible, but most games, I end up not doing much damage to the enemy champions. I normally go critplank with some tank at the end of my build. I need help with a good build and what masteries to take on him.
My current build:
Starting Items=
Main Items=
Ult upgrades=
UnboundHades1 votesfill your house with barrels your now a gp god
Åeolus1 votesUse practice tool. Make sure you can do al his combos before playing him.
JustJayson1 votesIt takes some practice to get the timing to detonate linked kegs 1 and 2 while adding a third after the 1st keg has exploded etc.. I am not very good at it myself, but i believe there should be some youtube videos explaining proper keg placement during laning phase and the combos.
Silly Neeko1 votesOne big issue most Gangplanks have is they use their Q on the barrel AFTER it gets to 1. This results in the barrel often times being converted to gold by the enemy laner.
For best results in fast placed barrel explosions, shoot your Q near the end of the 2nd health bar. Time it so that when your Q would hit, it hits less than .5 sec after it gets to 1. The enemy if any range will do this as well so it becomes a "first shoot first score" kinda deal.
EDIT:
Also, do the rapid cannon dropping first. More effective than the cannonball for the ulti upgrade.
Test out AP GP and Tank GP to see the funky stuff you can do thats just funny if the enemy is not expecting it...... Such as Titanic Hydra activation then Qing a barrel or enemy champion lol
Mizuki Zahra1 votesya barrel placement like if your top lane on the red buff top then you can place your barrel above tower to "hide it" I have seen Dayrus do this multiple times, he plays a lot of gp and I have picked up a few things from twitch lol
Sahn Uzal1 votes1 Practice. He's a hard champion and will take time to get good at, spamming combos in practice mode can help a lot https://www.youtube.com/watch?v=c2k8Q2WrE0Y This video should be able to help ya out.
Focus on
2 Don't just build one build, Gangplank's itemisation is extremely diverse.
Just make sure you rush , and then build whatever after.
I would recommend taking 10% CDR in Runes, so you can reach 40% with Trinity Force, Runes and Ghostblade or CDR boots or whatever CDR item you decide to build.
You can try full Crit GP 
A slightly more tanky variation 
Korean Bruiser GP 
For starting items, give these a shot
Also, if you play Toplane, you can build a Dorans Blade (Maybe even a Dorans Blade + a Cull) to get some more lane presence.
See what you like!
You get the point, GP can build a litteral ass ton of items, make use of that. is the best ult upgrade in for picking people off or nuking a single priority target
is the best for high teamfight potential
get this thing last.
leko bel zet 1 votes