Gangplank is a pirate. Therefore he must pillage all the booty he can. With this guide you will know how to Rob and empty yer enemy's coffers for optimal money makin'.

Of course, you will need Maximum Money Makin' runes (MMM runes) so you can always be makin money. Take the tickle magic runes so you can laugh at whatever damage they try to deal to you, and the Murderer runes to murder anyone for their money.
This will allow you to get money while getting money effectively getting you more money. These are a must.

This is very obvious, you will need to take Improved Teleport and Smite, for that will make you get to lanes faster, making you make money faster, and grant you even more money per kill. You will take Increased Mana regen to use your moneymaker ability even more and improved recall to get back to base faster to buy money making items faster.
Take 2 points into wanderer, you want to get back to makin money fast, and 3 points into Spell hack, to have no cooldown timer on your Map hack and Damage hack.
You will take 4 points into money grabbin and 2 points into treasure mapping, as well as 1 point in piracy, allowing for max money making. You will also take some extra damage to make the money making EVEN EASIER.
Making money while making money while making money.

Of course, making money can be a little bit hard.

WHO SAID THAT?
Making money is the easiest thing ever! Grab your starting gold and get the components for a philosopher stone. When you reach 330 gold press B, by the time you get back you should already have the gold needed for a philosopher's stone. Buy it and teleport to your lane, wasting no money making time whatsoever.

When you reach 750 gold go back again and buy an avarice blade, and go make even more money! Remember, everytime you kill a minion you get their money, but since you're a Pirate! you will get double money per minion! Go kill those guys and go back once again when you can buy the cool blue knife, the last item of our build.
EDIT:
Yarr! Avarice blade now gives an extra piece of gold per 10 seconds! Go pillage mateys!

Sadly, the enemies are far too stupid and will not surrender to your superior money making abilities, therefore you must buy some blue shoes, Triforce and Life Hack. If they still dont surrender sell your rad golden sword for a damage hack blade (Infinity Edge) and the cool blue knife for the Megadeath red Blade (Bloodthirster) OORRRRRR the hyper slayer (Hydra)[as suggested by Baiame EUW]. Dont sell the stone though, its the best item in the game.

Of course, you must take a point in your moneymaker everytime you can, because it makes more money and kills more, whats not to like? Also get a point in your long range money maker whenever you can, this will double all the money you make from level 6. The other skills are mainly used for not caring about boring cc's and running fast to kill that minion that may have ran away without giving you his lunch money.

Take the best spells in the game. Damage hack and Map hack.
Damage hack lets you nuke any minion, instantly becoming so awesome that you get their money plus some free awesomeness money. Map hack allows you to be everywhere to kill everything, getting all the money you can.

Of course, you will need a crucial ally to help you in your quest for booty (Arrr).
Who else but the Cardmaster, his passive gives you even more money and he has Map hack for his ultimate, forming a money makin duo with you. (You're much better, just don't tell him).

Pros:

You are a pirate
You shoot stuff
You get money when you shoot stuff
You get even more money if the stuff you shot dies
You acquire currency.

Cons:

The world only has a certain amount of money, therefore it is impossible to get infinite money (unfortunately). Too bad.

Start the game. Call top. Go top. Q --> Q --> Q --> Q. Repeat until money has been made. Buy more money makers. Go make money. When you reach level 6, use ur ultimate on any lane that has a lot of minions (except your own). Tell the card master to use his map hack to help you murder your lane opponent to steal his money.

Repeat till you have Tons of Money.

Win

Q - Parrrley - Allows you to shoot stuff, and get loads of money if you kill the stuff. You're a pirate after all.

W - Remove Scurvy - This skill makes everything K. Enemy attacks you? Press W. Felling not ok? press W. Enemy trying to slow you down so you dont get money? Press W, kill him, go make money.

E - Raise Morale - This allows you to move much faster and kill much faster, increasing your money making even further. Press E to increase it even more.

R - The ultimate money maker (Cannon Barrage) - This skill makes money in a huge area and can be targeted ANYWHERE. Thats right. Feeling sick to go make money? Press R, press W, use Map hack, BAM double lane farming, double moneymaking. This is the best skill in the game.

Speaks for iteself. Viewer discretion is advised (Rated ARRR).
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