Ok, so I'm going to be blunt about this. Gangplank is best when going for crit damage and chance. It goes with "Parrrley" well considering it already has a crit chance effect, and it also helps to get attack speed and movement speed so that you get an even better effect from the bonus in "Raise Morale". I start with "Dagger" because the extra attack speed gives you a greater chance to kill more minions, earning you more gold faster. Then upgrading the first "Dagger" I've bought to "Berserker's Greaves" gives not only a 25% increase in attack speed, but also Enhanced Movement 2, which gives about an 80-82 speed increase. This done, keep getting "Dagger" in pairs of 2 if you can, then build to "Zeal" and finally "Phantom Dancer".

Repeat the Process to build "Phantom Dancer" until you have 4, but vary up what you get as your gold count permits. Once you have the twin "Daggers", get "Zeal" if you can, or get "Brawler's Gloves" for the 18% critical strike increase, which will eventually build to "Zeal" anyway. Once that's done, if you have enough gold, buy "Phantom Dancer" or if not enough, get the "Cloak of Agility" to increase your critical strike by another 25% percent. By this point, you only need another 400 gold to buy "Phantom Dancer". Keep continuing this method of buying to get the "Phantom Dancers" that are suggested. By the time you have bought these 5 items, you'll have about 556 movement speed, 2.50 attack speed, and something like 124 attack damage.

Next comes the "Infinity Edge". This item is a legendary item, and as such costs quite a bit. Since you only have one item space left, it's best to buy the "B.F. Sword" to start off the build. Because you only have the one space, this is a good choice since it costs roughly half of the entire "Infinity Edge" price anyway, and gives 45 attack damage. From there, save up gold until you have enough for the remaining 2185 gold on the item. After you've finished buying the "Infinity Edge", you can be practically unstoppable!

The first time I used this build, I had 21 kills, and only one death. I dominated the game, and you can too. I know my masteries and runes aren't quite all there, but I'm only a level 19 currently. If anyone has any suggestions for runes to go with this build, I'm open to hearing them.