His latest buff has been amazing to him, I haven't lost one game and even got a quadra kill with him.

You still build him as a tanky mage as before. My typical build as follows

Dorans Shield
Boots 1
Regrowth Pendant
Regrowth Pendant
Sorc Boots
Force of Nature
Sunfire
Rylai's
either a Abyssal Scepter (if there are a lot of mages giving me problems) or Randuins Omen (for meele dps)
Finish with Guardian Angel.

Farm. Always be farming, unless theres a 5 man push down in mid, ignore it. You can carry games very easily if you can get items in such a short period of time. Always max out E as follows, then W, Q, and your R whenever it's up. HARRASS. I find he does amazing harassment now these days, it's key into shutting down a lane.

edit: pic couldn't be smaller ><

Depends on the team, my usual route is:
Doran's Shield
Sorcerer's Boots
Heart of Gold
(sometimes) Kage's Pick
(sometimes) Haunting Guise
Abyssal Scepter
Rylai's Scepter
Deathcap
Randuin's Omen
(sometimes) Deathfire Grasp
more so situational item

Not Sunfire, you want more damage from your spells so therefore AP.
Force of Nature is nice as a 5th or 6th item, not something to be rushed.
Guardian's Angel and Will of the Ancients aren't bad ideas depending on the team comp.

He's a melee mage.