Well i think full ap is good build mostly on 3vs3, you got much hp and hit hard by spells. I use this build for 3 days and it seems like preety nice.

well i dont got yet them all but with half of them its preety easy to kill your oponents and helps much specialy on start :).

after you got all these items you re selling dorian ring and than you got place for next, last item warmogs armor.

you can always exchange any of theese items if you hardly need magic resists or armor but i think you will not;p.

well its easier to play with extra stun - exhaust and flash - to run after or before somebody.
theese 2 spells are most profitable in late game - in my opinion.

please comment this build and tell me if i can change anything or if its good;p. would be nice to hear some extra ideas about playing with other items, runes, skills.