First of all you should know, that Gangplank is great for ganking. His jungle way is pretty easy and killing gangplank needs a lot of damage, later in the game.

For runes i take typical meele dps runes, but it's also possible to change and still getting a great result.

In the jungle you start with the vampiric scpeter. After the first time going back, you get cloth armor and a heal pot. Later on for more gankability, you get the boots of speed and after that wriggle's lantern. For a little bit more damage you buy sheen. From now on you become more and more a tank. The next Item should be the giant's belt and after that you complete it to a warmog's. Now get a the cloak of a agility or a chain vest. That depends on if you need more damage or more defense. Now get Atma's and you will deal very high damage and, because of the warmog's, you can also tank very well. Finish Tri Force and after that for more damage get infinity edge, or if it's needed, get another defense iteam (sunfire cape, etc.)!

Start: Wolves
Wraiths (smite the big one)
Golems
After first back: Wolves
If there's no opprtunity to gank go on with
Blue Buff
Go back to the base if there's still no gank opportunity and after that: Wraiths
Look if there is a gank opprtunity, if not
Red Buff

Just look up to the top. For the jungle you need Raise Morale, just use it 1 time for the wolves. After smiting the big blue wraith, skill Parrrley. From now on the jungle is pretty easy.

All in all I would say, Gangplank RULES!!!