I noticed alot of gangplank's that do a crazy amount of damage, But cannot take alot, So i tried to make a tanky Gangplank, Which was for fun one time, and it worked. All the items in here work perfectly, What i noticed, All you really need is the Infinity Edge to do the main damage, Which are huge crits. In this build, I will further explain the somewhat steps to it, As you read on. Enjoy :D

Well, I like to rush Infinity Edge in the beginning, I start with Brawlers Gloves and 2 Health pots, Into an Avarice Blade, Then my boots of Ionian Ludicy, Then another avarice blade. With the crit and more gold accumilation, The infinity edge can come quite quickly, Especially with Gankplank's big laning precense. Once i have around enough, For Infinity Edge, I sell one avarice blade, Or you can later on, Eventually you sell both, It's just to start off, After Infinity Edge, The fun part comes in, The tank items. I start off with Thornmail, Then i put in spirit visage next, Which was amazing, It's health, Cooldown Reduction, And it makes my Heal
(Remove Scurvy) Heal me for even more, It's somewhat an essential item, Then i get a Force Of Nature, Of course you need some Magic Resistance, Plus health Regeneration, Which is really nice and the movement speed that most players are used to from Phantom Dancer, And to finish it off A Frozen Maller, It's More AD to the build, A slow, and Health, You end up with Very nice Survivability rating, And still Mass damage.

There's not too much to know about Gangplank, His parrley Is such a vital laning ability, It can crit so constantly, And it is ranged. If you have a long game, When you have the full build, You can see a really OP Gangplank, The main reason is you can survive for so long, And almost 2 shot Other Champions at times.

Quints: Well I usually go 3 Desolation, I put in two, Mainly because One quint Of Furor, It reall effects Early game.

Marks: 9 Marks of Desolation Is extramely vital, The armor pen is so nice

Seals: I tried to balance out the Crit Chance and Crit Damage, And i also threw in one Evasion, I know it's a bit strange, But i like champs that always can have that little percentage of dodge, That can save you in meny situations.

Glyph's: I went 9 Glyph's of Celerity, More cooldown reduction is very nice

Overall It's seems quite balanced.

The masterie's In the build are basic. Arm pen, Cripple and Haste, For your Ghost and Exhaust, More experience gained, ect..