VIDEO COMING SOON!

PRE-NOTE FOR EVERYONE:
Apparently someone is starting a downvote campaign because they believe I have "cheated" the system by making accounts to upvote my build. This is completely false. You can read the comments and see a Moderator has backed me up on this.
People whom I have played with asked me how I built GangPlank since they liked how I play, so I decided to write this guide for them and for all of MobaFire users.
If you don't like my build, feel free to leave constructive criticism as to why, and I will take it gladly. But I ask you to try it before you knock it.
Thanks- VillainGuy

Welcome to my first build on Mobafire, and welcome to SlowPlank!
Basically this build focuses on amplifying GangPlank's new passive, and making it IMPOSSIBLE for the other team to get away.
Basically Gangplank's new passive, in my opinion, makes it so he should be built differently.
Not just to help your team, but to make you the ultimate carry.
The build gives you survivability, damage, and all around chase/escape mastery.

Now on to the guide!

I went with nine Armor Pen Marks Greater Mark Of Desolation, as 15 ARP is a great start, and will help you chew through squishies.

For seals, I went with nine Flat Armor Seals , this gives you a great start to survivability, and makes it so you can get up close and personal with the enemy team.

For glyphs, I went with nine Magic Resist Per Level Glyphs
Again, even more survivability, helping you keep a good guard against those pesky casters.

Now for the most important of all the runes. Movement Speed Quints.

Why are these so important? Your job as SlowPlank will be closing the gap on other players, and making sure they are going nowhere. With Remove Scurvy, you should always be able to chase someone down after you get boots/Frozen Mallet.
Mixed with your slow and Raise Morale? They will have no escape from the almighty SlowPlank.

Masteries I take a different path than most, and I go with 21/9/0 with GangPlank.
The 21 in offense gives you the crit chance, cooldown reduction, and all the damage you need.

Why 9 in defense?
Again, this build is for closing the gap, and getting up close and personal with GangPlank.
No one should ever be able to run from you, and if you have good defense? They can't turn around to try to kill you either.
Defense is key, and the points in the HP/5 from mana just help on top of your Philosopher's Stone early on.

Now with this guide, I have laid out pretty much the exact steps you should take, and it will get you far.

Start the game with Brawlers Gloves and 1x & 1x

This gets you a little crit off the bat, and helps build into your

Why and Philosopher's Stone?

Well, Gangplank is a money making machine, with Parley giving extra gold, why not add on top of that with two gold per 5 items that will help with crit, and even more survivability?

As for boots, I believe are the best fit, as it gives you excellent map coverage, and can get you to team fights in a jiffy with your Raise Morale. The movement speed you get from quints+boots+morale is almost 600. It's pretty ridiculous.

However, some people have recommended .
CDR is awesome on GangPlank as lower cooldown on Parley/Ulti=More Damage.
However, I'm a bigger fan of complete map control, and basically being there for every fight.
As you can see above in my recent matches, my assists are always high, because I'm either there for every fight, or my ulti is (I will go into this in another section.)
So boots are of course your preference.

Now here is a KEY part of your build:
Why so important?
Your passive (this hasn't been updated on MobaFire yet as it is a new patch,) added on top of Frozen Mallet's 30/40% slow is disgusting.
You can Parley, then run in close and start melee, and they will never get away.
It also gives you survivability with the great amount of health that it gives!

Next is:
I've since updated my build, as I didn't realize how good Trinity Force was on GangPlank. Silly me.
This gives you HP, Mana, Damage, MoveSpeed, and the passive proc is just awesome for Parrrley as it applies it to the actual shot.

After that:
Phantom Dancer just adds even more movement speed/attack speed/crit chance, which is amazing for those crits/chasing.
However you could go
before the Phantom, especially if you feel you're lacking in damage (which by this point you shouldn't be.)
Honestly you can swap those around as you see fit.

If the enemy team is stacking armor?

Regardless you should either get a or if you need a quick route out get an as the Crit Chance, LifeSteal, and Passive (Stacks with each hit, which works really well for this GP build,) are just a wonderful addition.

As with any guide/team, after the core items make sure to build accordingly to what their team is doing.

Pretty simple, max first for the extra gold (combined with Avarice and Philosophers? You're a gold earning BOSS.)
After that max
Of course max whenever possible, and max last.

So after you head off to your lane with your and potions, get started on last hitting like a BOSS.
Use as much as possible to last hit, and if the enemy team in your lane gets pushy? Use it to do some damage.

Now, if you have a competent laning mate, and are having a strong harass early on? Don't be afraid to pop that exhaust on them, Parley and start laying into them. The slow will keep them long enough for you to most likely get a kill, and usually get you first blood as well.

This is how it goes for your first back, either wait till you have 1150 (To finish and make a Philosopher's Stone)
Or, alternatively, if you are having a strong laning phase/got a kill or two, back when you have 1500 to get ,Philosopher's Stone, and

That combo will keep you in lane for a very long time, and the Avarice gives just enough crit to help with early harass.

Alright so this is where I will explain to you exactly what your role should be in not just team fights, but in the whole game.
I would definitely say that GangPlank is more of a bruiser/closer than he was before, and I would definitely capitalize on that.

First off, you should always be aggressive right after a crit. Let's say you're in lane against two seemingly tough champs, and then all of a sudden BAM! Your Parley crits for a healthy chunk of damage.
The enemy will most likely back off, but some of your enemies are not that smart, or have not met a competent/skilled Gangplank before. So what I usually do is right after I land that crit?
Exhaust, and start wailing on them. Most of the time it will end up in a kill, as your damage+slow is quite good early game, and just dominating late game.

Usually your skill combo in a fight will be E>Q>Attack>Q. Keep your E for when the enemy tries to exhaust/stun/snare you. However, remember when facing heavy CC teams, a LOT of them will have some sort of stun or slow, and you should wait to use Remove Scurvy until the last possible moment to maximize escape.

Now here is the #1 thing you should take from this guide, and that is

ALWAYS BE MAP/TEAM AWARE.

You have a global ulti with a relatively low cooldown, UTILIZE IT IN ALMOST EVERY TEAM FIGHT!
Remember, while it may not always get you a kill, it will ALWAYS assist your team in one way or another!

See that? Most assists, most kills, least deaths. This should be about how most of your GP games should go.
Why most assists? What you see above. Being map aware is completely key. If you're not there for a fight? Your ulti should be.
If you're not hitting someone in a fight?
Raise Morale should be helping your team get them.

What you don't see in that picture? Is most of those deaths were early game. I solo laned vs. an Ezreal who hit level 3 somehow before I hit level 2. But I stuck it out, played it safe, built my items and guess what? I won in the end because of superior playstyle, and better teamwork.

The key to Gangplank's ulti is placement and timing. A perfectly placed GP ult can completely change a team fight around, and possibly turn a loss into a win.
One of my favorite things to do is wait for the enemy team to chase my team into the jungle, and then pop my ult right on top of them. They will be slowed with limited mobility because of the jungle, and it will completely wreck.
Also, if you know where someone is running and they have less than 3 bars of health left? Ulti them.
I have gotten a lot of cleanup kills this way, and it is basically free gold/xp for you!

Did I mention how awesome Remove Scurvy is? It is basically a free cleanse on a relatively short cooldown. Malz ulti on you? Remove Scurvy. Warwick suppressing you? Remove Scurvy.
It is an amazing skill that makes Gangplank such a great chaser/escape artist.
The great thing about going with Boots of Mobility is, if you can keep them from hitting you for the amount of time it takes to get out of combat? They will not catch you.

In team fights your role is a difficult one. If you get a good crit off, or if their squishy is out front? Initiate like a boss, especially under your ulti. Your ulti is not just a great closer, but an excellent initiator. Pop the ulti right at the edge of their closest champ, and they will have nowhere to go but through it.
Anyone going through your ulti you should immediately hop on and DPS down.

The ulti can also change a situation completely. For example, in my last game as GP an Ezreal and I were getting chased down after a team fight by two near full health champs, but we were both struggling. As they chased me, I placed my ulti right at their feet, and as per usual they got half-way through and tried to turn around, and this is where I told my teammate to move with me. We made the situation turn in our favor by switching their mindset from "Oh we're so gonna get these guys" to "****, I've taken too much damage and I should run."
This is the perfect situation for Gangplank as nobody runs from Slowplank, nobody.

Pros:
Strong fighter
Amazing slow
Ridiculous Damage
Excellent Chaser/Runner
The best slow since Nasus

Cons:
Even with this build, still not invincible :-P
Mana hungry before Philosopher's
Doesn't melt face completely before IE

All in all this build is made for suppressing the enemy team and making sure they can't run away if you're in a team fight. You will dish out massive amounts of damage, especially late game, and they will not be able to escape you.
As with any build, it doesn't matter how well you play or how well you carry, you need a good team to help you out. While GangPlank can do major work to enemy teams, he isn't perfect, and can't win every game.

But try out this build and you will see, SlowPlank is the BestPlank.