Pros:
FARMER
huge AOE damage
Stun
and again farmer

Cons:
extremely squishy

Hey,

this is my first guide, so tsay what you like and what i can do better. I will just throw this guide out there and then go on vacation the next 2 weeks, then i will try to change what you didn't like and i will probably add some more builds i tested on him.
Right now i am trying to play him on CD and spell Vamp, but i didn't find a good build yet.

Marks, Quintessences and Glyphs are self explaining, you are a mage.
for Seals i take health per level, because no matter where you are you are estremely squishy. Well you could say thats just some health, why not take some more damage. Well health is a primary rune here and helps out more, especially when you are laning mid.

Well, here i take some more magic pen.,some mana regenaration and some CD. And always add the 2 points Utility Mastry, cause with this build you will need the mana Golem.

The Items, here i take mejais first. Then boots and then i rush rabadons deathcap. After that i go for some life and the nice slow from Rylais(If you feel like you die a lot go for Rylais first, since it will give you a lot of health). Then the Hourglass, which will save your life several times, since you cast your combo then go invincible and when there is still somebody alive...the combo again.
The last item depends on the enemy team. Either take Void staff if the stack Magic resist. Take another rylais or andother deathcap... I don't know yet, because i didn't get to that point yet. After the Hourglass the match was pretty much over.

Here you take every skill first and the focus on your w since its your strongest skill. Then you skill your e which will destroy the minions waves that are coming. Then your Q, your stun. And don't forget your Ultimate, which will be really helpfull once you get into Teamfights.

Yeah... what about FARMING. With this Champ farm, farm and don't forget to FARM. He is a farming BEAST. And he needs the farm. Thats alos why you take Teleport. you go on one lane kill the minions with two...or one attack (w) and then you port to the other lane and do the same again. I personally havn't ended a game without about 200 Minion kills.