Gangplank is an amazing solo-top, jungler and ganker.
ive played numerous ranked games with this good ol' pirate and thought, lets give him a guide.

Runes
Standard carry solo-top runes:
Armor Penetration Marks & Quints
Armor Seals
Mres Glyphs

Masteries
21/0/9
Standard mana-carry loadout, 21 points in offence and 9 in utility
focussing mainly on high damage and proper mana regeneration.

The basic's of Gangplank's skill uses
Passive - Grog Soaked Blade slow, damage, it's great for last hitting and chasing.

Q - Parrrley is a hard poke with on hit effect's, activating Frozen Mallet and Trinity Force

W - Remove Scurvy save's your life, because it removes any cc and debuff on you

E - Raise Morale attack speed and damage increases pasively and activating it gives more movement speed and damage, a getaway or chase skill

R - Cannon Barrage is great for farming, picking up low enemy's and slowing and damaging enemy's in teamfights.

Why not rush Infinity Edge?
Because your survivability will be 0. you need the life steal, sight ward and armor from Wriggle's Lantern

Philosopher's stone
After a while you wont need it anymore and you can simply sell it and get a Frozen Mallet instead, for more health, damage and a extra slow besides you passive.

Possible Berserker's Greaves for Mercury's Treads
if you enemy's have a lot of cc like slow's and silence's you might want to get a Mercury's Treads because it will save you a lot of trouble.

Trinity Force for an Phantom Dancer or a Warmog's Armor
you can do this if you feel like more health or think Trinity Force is useless on Gangplank

Farming
As Gangplank farming is a piece of cake, Grog Soaked Blade can finish off just that little health on a minion if you miss the last hit and can slow your enemy's while you poke them repetively with Parrrley.

Solo Lane
Poke your enemy with basic attacks and Parrrley as much as possible, get them low, push them as much as you can and farm all the minions avalible.

Duo Lane
Try to lane with a support like Taric or a strong ranged dps as Caitlyn, Vayne or Ashe. because they all have cc than can stop enemy's like Dazzle and Yordle Snap Trap or slow enemy's like Frost Shot and Condemn so you can get as much early kills and lots of farming early on.

Area Controll
Gangplank has great area controll using his Cannon Barrage during teamfights, this can stop enemy's from coming to you while ganking or scare them away. try to activate Cannon Barrage during teamfights on top of the squishyest, as they can get low and flee.

Know your place
Gangplank is a squishyhunter. you get into a teamfight not head-in but with a small corner to get to the squishy and kill them.

You're mid
Tank/Major cc engages
team attack's head first
you take a walk around to the side brush
focus the squishy
enemy team dead? focus tank
ace or almost ace, if some got away

Gangplank is also a great chaser and chase-breaker
imagine:
your good friend Garen is low and is running away from Annie and Sona
you run in using Parrrley on Annie and also using Exhaust on her, you use Raise Morale and keep auto attacking Annie
Annie dies and Sona stuns you, you are low on hp now, Remove Scurvy saves you and you start auto attacking Sona, Parrrley and auto attacks make short work of her.

Bilgerat's!
This is a standart carry build for any dps, but it works great with Gangplank and i simply love how he can dominate lanes with his self heal Remove Scurvy and Cannon Barrage

Thanks for reading!