For runes:
+.87 magic pen x 9 (marks)
+.1 AP/level x 9 (seals)
+.17 AP/level x 9 (glyphs)
Masteries:
Offense:
3/4 Fury
4/4 Sorcery
4/4 Blast
3/3 Havoc
1/1 Arcane Knowledge
3/3 Mental Force
1/1 Spellsword
3/3 Sunder
4/4 Archmage
1/1 Executioner
Defense:
N/A
Utility:
3/3 Wanderer
Now onto the build.
What I do is start boots/3pots, and then I try to stay in lane until I have over 1200. If you have to back, buy an Amplifying tome (2 if you have enough), and pots (don't have more than 3). I rush the hell out of Hextech Revolver, because then you can have your spell vamp (and AP building later will benefit you greatly). With this sustain, you won't need to buy many more potions at all for the rest of laning phase. Use your W (spin with low cool down) for easy sustain on groups of minions. Next build towards Haunting Guise, and if I can only buy one part yet I will get the Ruby Crystal for extra health into later laning phase and beyond. Usually before I build Guise, I'll upAfter building Guise, go straight for Giants belt and build into Rylai's. You'll get your slow, and once you've that you can upgrade your Haunting Guise into Liandry's Torment (which does extra damage if they're under an effect). Once you've got Liandry's, start towards Abyssal, or Rabadons. I prefer to do Abyssal and save Rabadon's for late game, because you get magic resist and it gives an aura. Upgrade Revolver to Will of The Ancients if you feel like you need it somewhere in there by the way.