Hi. i'm LegendOfCroatia and this is my build for Gangplank and how i play with him. I hope it will help you ;)

For runes i pick 9 marks with +1,66 armor penetration, 9 seals with +1,41 armor, 9 glyphs with
-0,65% cooldowns and 3 quintessence with +4,5 magic resist. I pick This rune because you are stronger at the beginning.

For Masteries i pick 21 in offense, o in defense and 9 in utility. I recommend 21 points in offense because it's good that you have big damage and good critical chance.

When you buy Infinity Edgesell Doran's Shield. If you want you can instead of second infinity edge buy The Black Cleaver.

You must as fast as you can reach 6 level and start to raise your Parrrley skill because it's best skill of gangplank

For spells i pick fleshand ignite. Flesh to easyer escape or when chase someone to get closer to him. Ignite in the start is great in combination with Grog Soaked Bladeto deal many damage ;)... that is end thank you for using my build and pleas rate :D