AP / Gangplank is probably frowned upon by most players, but that's usually because they've never seen the build played correctly. It's one of the strongest lane controls and great support ( Not to mention an off-tank )

Pro's
One of the best laners
Makes a lot of gold fast
Great survivability


Con's
Low damage
No neutral escape skill

I will sum it up and make it short and sweet.

Start with a mana manipulator
The mana regen will make you last in lane Until either you die or want to spend your gold.
Last shot every minion with parrley
This is what brings in all the gold, the mana cost isn't a big deal.
It is recommended to bot lane
Your a great support and you take sponge all the damage.

Follow the items listed within the top of the page, If you are doing bad get your Warmogs before your Hourglass. Get Guinsoo for the extra Attack damage for parrley, that way you can harass more and last shot minions a lot easier.
Eventually you can harass opponents with your constant parrleys.