Well, the monkey king is and great but nasty character because it takes a lot of damage
i start with and critic item to bonus his crit but you can start with the dagger to hit faster and pursuit easily to the boots, then going to attack speed and critic buying the zeal, going next to the damage with a infinity that Boosts the critic damage and the critic, giving more damage, then you can buy life steal since you have a good speed now, buying the bloodthirster, then you pursuit the phantom to basiclly "end" the game since you are hitting too fast, taking too much damage and stealing too much life, becoming a Threat to the enemy team, after that you can Buy an Black cleaver or beggining to build items like warmog to ultimate your "War Monkey Machine"

The runes aren't the correct's i think, but they boost a lot