In this Guide I will show you exactly how I build my famous GP build.
First here is a video I would like to show you about the capability of Gangplank:
1v5 Pentakill!:
Play Video

Let's discuss the Runes:
An excellent Mark, early game critical chance supplies you with both early game Quick Kills and Mid game Survivability.
The seal is compatible with your Crit chance supplying an even higher chance at the same benefits!
The same benefits as the mark, only on a slightly smaller scale!
+13% Crit damage! That added onto the 50% bonus from Infinity Edge is equal to 263% crit damage at a very high crit rate! Tons of Damage!

There is nothing really to say about my mastery tree, it is how the mastery tree should look!

Boots and Health Potion shortly followed by 1 or 2 Doran's Blade is a great way of starting the game in terms of early-game kills and survivability.