I take flat ability power runes for the time bomb explosion damage. This gives me a late game 2 hit kill with time bomb.
I take 9-0-21 for increased ability power in offense and cooldown reduction masteries in utility.
For items i start out with boots of speed and a blasting wand. Upgrading boots of speed to sorceres shoes and blasting wand into a rabadons deathcap. Then i grap a zhonyas hourglass and a rylais crystal scepter increasing my damage out put and health even furter. For my final items i take void staff and deathfire grasp, making sure to remember the active of deathfire grasp.
This is the ultimate equence granting you a kill against any non-tanky champs if full builded and sometimes even when not full builded.
I use this in team fights when focusing targets caoturing points and still looking out for my team mates to make sure we will have the most positive outcome of the battle.
I take ghost to get to locations quickly and capture most points.
I take promote because pushing minion waves will surely get you a point if using promote at the right time (When your minions start to capture).