In early you want to focus on stacking.You should to come to base with 1300k gold or more.
After 6 lvl you should roam with your jungle and take kills. You are able to kill your lane enemy if he is not feeded.

You still should stack if you can. Still roam with your jng. In team fights try to stun adc/mid. You have low cd on w so don't be scared to use it.

In late game you can kill everybody. If you die in team fight its huge chance that your team will lose tf or even lose game. Ult the most feeded enemy champion in game. You have very low cd on w and huge dmg so use it when you can.

Why should I take these runes?
Manaflow band - give you more mana so you can stack more.
Absolute focus - if you hit your e in late game with full hp you have 100% chance to kill sb.
Gathering storm - gives you more ap. Who don't want more ap?
Biscuit delivery + Time wrap tonic - these biscuits can save your life and let you stack more.

Zhyonia - you can survive when you play vs assassins.
Luden's Echo - give you mana regeneration and ap.
Sorcerer shoes - give you 18 magic penetration.
Rabadon - give you even more ap (scale with stacks).
Mejai - take it when you have a lot of kills and you are sure you wont die.
Banshee - let you survive when you play vs heavy ap's.
Void staff - even more magic penetration. Take vs tanks.
Hextech protobelt - take when you need more hp.
Morello - give you a lot of ap and magic penetration.

Pros:
+Delete any champion
+Stun
+Low cd on w in late
+Infinity ap
+Ability to solo carry

Cons:
-Squishy
-Weak early
-Can't escape
-Long cd in early

I hope you enjoyed my build and you will go to gold this season (or even more )
See you in next guides.
Have fun and good luck :)