We buy the Saphire crystal because Gankplank have in the early game mana problems and the two potions for situations with low HP. Ninja Tabi is very effectively because he doge a lot of damage and less damage is more survie or more chance for an kill. Infinity Edge it explains itself. Trinity Force is an wonderful continuation of sheen and it gives a lot of helpful atributes. Phantom Dancer is always god to have more attack speed and critt is the important atribute for gangplank.

PARRRLEY is an good skill to hurras the enemies we can use it often because we have our Saphire crystal.

REMOVE SCURVY is an very importand skill for Gangplank because when we in a fight and the enemy have a lil bit more HP we use our REMOVE SCURVY and we winn the fight without of problems.

RAISE MORALE is an nice skill for pushing and ganks the attack and movement speed is a very good support in situations like a gank or an escape.

CANNON BARRAGE this skill is very effective when the enemy have low hp and run or be beside the tower we cast the skill and the enemy is dead and again in team fights, escapes and a lot of other situations very helpful