Ohai. I see you've found this guide to Gangplank. Gangplank was the first champion i bought and I've been maining with him for a long while now. In this guide I'll show you how i play Gangplank and carry my team to victory

Pros

AMAZING burst damage with Parrley.
Ult slows to get out of sticky situations.
Can eat oranges and make everything K.
Damage increase to shred down turrets.

Cons

Pretty squishy
Always focused
W has fairly long cooldown
Can be very mana hungry early game

I grab Brute Strength for some more damage early game. Alacrity gives some useful attack speed. Weapon Expertise, Lethality, and Sunder plus my runes are great for destroying your enemy early game. Deadliness helps with damage late game. And Executioner mixed with ignite helps take down enemies. Resistance, Hardiness, and Durability keep your from death in tough situations.

Well my runes are pretty simple. I take damage Glyphs,Quints, Marks,and Seals for the extra damage along with some armor pen and crit chance for early game dominance. Pretty much my standard ADC rune page

I start with the standard boots/pots. Then i start my Infinity Edge form some damage and crit. But then i get a Berserker's Grieves and a Zeal for some attack speed. A Vamp Scepter will give you some sustain in lane. Finish the I.E. for damage a crit, then complete your Phantom Dancer and start another for some attack speed, and a tad bit of movement speed. Next, finsh your Bloodthirster and try as quickly as possible to stack it for even more damage. Your next Phantom Dancer will give you enough Attack Speed and crit to destroy enemies in seconds. Finally, a Black Cleaver will give you even more Attack Speed and damage, mixed with its passive, and you will be unstopable with protection by your team.

Gangplanks passive is Grog Soaked Blade. When GP hits an enemy with an ability or basic attack is does a small amount of damage over time and applies a slow. Don't fall back on this for kills but the slow will really help you catch up to a fleeing enemy.
Gangplanks Q is Parrley. This attack has a 1.0 scale with your AD and mixed with crit will be your main damage dealer because it also applied on hit effects. I max with as soon as possible for maximum poke and damage. If you feel like wasting mana then this ability will also give GP a gold bonus when he kills an enemy minion/champion with it, which can be useful for farming.
Next is Remove Scurvy. This heals for a small portion, but more importantly it will remove all debuffs. Use this if you get slowed, stuned, or anything else to get out unharmed.
Next we have Raise Morale. This passively gives GP more damage. When activated it increases his damage and movement speed and any friendly champion nearby will get half the benifits that Gangplank gets. This mixed with Remove Scurvy can speed you up to get away from any chasing enemies.
Finally, Gangplanks ult is Cannon Barrage. This causes Gangplanks ship to fire on any location on the map. This can be used to check, or steal, Baron/Dragon. It can also be used to scare the enemy team off a turret as you run back. Also,you can fire it on yourself in a team fight for extra damage or while running away because it will also slow the enemy team and hopefully make them give up the chase.

Really Flash and Ignite are all I use on GP. I guess Ghost or Heal could be switched in if you want but other than that you really shouldn't be using anything else.

In a team fight GP should be towards the outside. He can poke with Parrley or Cannon Barrage and can lead a charge to focus down the ADC on the other team. But that should be avoided. Try and hit someone with Parrley and to get them slowed then have your whole team focus them down. When taking Baron or Dragon use your E to help your team get it faster. Gangplank fights for his friends so dont be afraid to use your ult to help a teammate get away.

So, that is just about it. Using this build/guide to GP i have been very successful with him and I hope that you too will have success with him. Feel free to comment and vote up to help me improve this guide.
K. Bye