As a gangplank player, the easiest way to kill him is to simply chain two or more crowd-control effects on him and get your ADC to delete him from a distance since his barrels have a priming time. Gangplanks damage is mostly barrels and skill chains from Q/Ult.
If he's not level 13 or higher = You'll often win a trade. After 13, his barrels prime extremely fast. your goal then is to ignore the champion, kill his barrels.
THE EASIEST WAY TO GET RID OF BARRELS...
If he is level 13 or higher: After the first bar has ticked down (barrel placed, .5 seconds later), immediately strike and often your attack will land right as the third tick arrives -- destroying the barrel. The moment he's lacking in his burst, you can often dive him and the most he can do is Auto-Q-Ult.
If he's above 7 < 13: Barrels tick every 1 second. After the barrel has been placed, allow 1 tick to occur. After that, press in if you're melee -- fake one auto attack on the barrel (auto attack cancel to bait him to 'assume' you'll hit it to activate it early), then follow up with an auto to destroy it. as a ranged character it's much easier to do this.
If he's below 7: The easiest time to counter him, as his barrel recharge rate takes a LONG time -- if you destroy his barrels he has to wait a long time to get them back. Be aware -- The moment he levels his E for the first time, he gets 3 barrels for free! Expect him to look for a chain. Most often, a good GP will..
Lay the barrel, immediately auto attack it, and it will prime in 2 seconds. The easiest way to counter this is to simply pressure him to either choose hitting YOU, or the creep wave..Or, simply auto attacking it twice early -- his AA speed is pretty slow early on.
All in all, the best way to kill GP is to all-in him before he can use his barrels, which forces him to run away, or burn his Q on you rather than the barrel that'll chunk through 40% of your health. Bad GP's are very apparent, and good GP's are, too. GP relies solely on his W to remove a vital crowd control, and his high movement speed from detonating barrels. Get rid of the barrels..There goes his mobility, meaning he's dead in the water.
ahem
