Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This Gangplank build relies on crit chance. Once you have everything you crit at level 18 will be 100%.. With this build your sure to be able to handle any enemy Legend that comes your way. Now the order in which you get your moves can be modified to the situation and preference. Other than that everything should be pretty sure fire. Using exhaust and ignite will ensure you get that last hit before the enemy gets gets away. Especially good against Master Yi, Shen and Ashe. Given that you don't have much armor the dodge chance you get helps make up for it. I hope you have much success with this build. Good Luck and give me plenty of feedback.