This is my first build, but is a very effective build. Gangplank is the only champs that i know of that has a skill that can get a critical. This build takes that skill and raises it to new heights, while you reach deadly critical heights. This Gangplank build is a very powerful build late game, if you can build stuff fast enough it can help your team out mid game. The way this build works is you critical they die simple as that. When chasing down a enemy champ the update to Gangplanks passive, really helps out because now it slows with every-hit and not reduce the healing they receive. Gangplank is a big carry in any game as when he gets items his damage goes way up, on his Parrley and on his ultimate when you get some Ability power.

Pros
Your critials hurt like Hell
You have decent movement speed can help your team out.
Your Q skill gets you more money.
Has a Self Heal that heals quite a bit

Cons
Expensive build
Takes a while to get going.
Cool downs are long at low levels

For Marks its the standard Armor Pen (410*9=3690 IP)

For Seals you want to get Seal of Furor, these runes are mostly for mid to late game but help early game as, with parrrrley lvl 1 you can critical up to 150 at lvl 1. (820*9=7380)

For Glyphs its the same as the Seals, they just make your critical hit hard for late. game(820*9=7380)

And the Quints just add more damage onto your critcal. (1025*3=3075)

This Rune page build is VERY, VERY expensive as it takes about 20k IP (3690+7380+7380+3075=21525 IP) to be exact

The Masteries are your standard Fighter style masteries, having more offensive masteries then others. Getting the increased Damage on minions mastery may seem slightly odd but it does help when u take into fact that Parrrley gives bonus gold when you kill something with it, many a time have i left a minion with just 2 or 3 health.

The Avarice Blade is a good help in getting your other items so i recommend keeping that till the very end.

When i was originally planning this build it was a stack of 4 Avarice blades, and just buying the Infinity Edge straight up, but with recent patches i had to change the whole build idea.

The Phantom dancer before the Infinity edge just helps u get around the map a little bit quicker, and maybe even get a few ganks in.

The Trinity force is a very helpful item as it has a chance to add a slow on hit, which parrley would add also, with both slows it very easy to take down even the tank of the other team. It also makes your Ultimate just a little bit stronger which is amazing with the recent patch, as it hits much harder.

The Second phantom dancer just adds a little bit for attack speed and critcal chance.

The Last Whisper is just for those pesky tank that have a lot of armor.

So the order is:
Brawler gloves->Avarice Blade
Get Boots
Cape of Agility->Phantom Dancer
B.F. Sword->Infinity Edge
Zeal->Trinity Force
Phantom Dancer (Make it anyway you want to)
(Sell)Avarice Blade to Buy a Pick Axe->Last Whisper

The Sequence that I have does not need to be fallowed at all. It is a very good build as you can help your team out also, with your E skill, but its just a suggestion, depending on the opposing team you may need to get your W skill faster, but its just a suggestion.

I choose ghost and exhaust, just for that fact that they are very helpful on any AD champ.

You could also use Teleport with Gangplank by dropping your Ultimate then teleporting into the area and take out the enemy if they are stupid enough to stay in the circle.

Gangplank is a good team champ as his E skill helps out every Ally champ around him. It gives your teammates move speed and attack damage by 50% of the amount that you receive. So a Master Yi that highlanders would also get a massive speed increase with your Raise Morale skill. Also In Team Fights his Ultimate can do a lot of Damage due to the recent patch that made it stronger.

Gangplanks Q skill is amazing for farming when your short on cash, as when u kill something with it you gain bonus gold. So Spam his Q skill on every weak minion there is. While his Q is his main farming tool his W also helps as it gives him some bonus damage and move speed.

This is my first build, might make more not sure, but please write any comments about the guide.

The Build is a pretty good build for Gangplank, its quite expensive because of the runes, but in game they help out a lot and the build is pretty average on price, because of his Q skill and he gets bonus gold with every kill when he uses it. The Runes that this build takes are very expensive, is 21.5k IP to get all of them, so if you want it start saving up now. As for the Masteries they can be very useful the way shown or they can even be useful with a different load out, but each person has their own ideas on how stuff should be made and this is mine. Gangplank is an all around good champion because his skills are no over powered like some but they deal a good amount of damage and still can hinder him. Thanks to everyone who reads this guide and comments on it, every comment can help me make this guide and any other guide i make better.