Not Updated For Current Season
This build gives tons of AP and Health. Try to get mid it really helps, i always dominate every game with this build and mid.
I start off with Amplifying Tome and a health pot and lane till I have 2500g and get Mejai's, boots, and a Giants Belt, if im forced to go back before i have 2500 i get Mejai's and a Giants Belt. From there just follow item build and you should have 600-700 ap along with 4000-5000 hp.
As for the last item i left it off cause it always depends for me. If your getting tons of stacks with Mejai's then i will get a Guardian Angle, if not I would most likely get another Rylai's or Abyssal Scepter, and a Void Staff if a lot has Magic Resist. With runes, boots and Masteries, the Void Staff would not reduce the enemies Magic Resist by a lot unless its Stacked.
If the game lasts even longer i sell boots and buy Elixirs of Fortitude and Brilliane and rebuy my boots, which ive done in many many games.