This is my first guide. With this build you will be able to jump in team fights and come out alive and also deliver a huge amount of damage. I hope you enjoy!

Here you will want to have 9 Magic pen Marks, 9 AP Glyphs, 9 AP Seals and 3 AP per level Quitessences. So basically after you build the sorcerer's shoes you will deliver a damage similar to true damage because your foes will have M. resist near 30.

Here you will want 9-0-21. The reason I chose the ignite mastery over the magic penetration one is because in early game since you will deliver almost true damage it wouldn't benefit you that much, so having +10 AP available will boost your performance.

Here you will want to make the M. pen boots followed by the rylai's scepter for slow HP and AP. Next you will make the zhonias hourglass. Why is this? Because having 4 seconds of ivunerability (sanguine pool + zhonias) will allow you to go into team fights and come back out alive delivering huge ammounts of damage. Next follows the abyssal scepter for AP and M resist and then void staff and rabaddon's death cap.

I chose this spells because with ignite and it's mastery you will get more AP and also the 14% of extra damage from your ultimate will boost your ignite damage. As for exhaust, I chose to prevent the enemy from escaping and dealing less damage to you. However, when you build up rylai's it won't be as necessary so I believe ignite is a must. And as for exhaust, if you like you can trade it with flash spell for more unexpected ganks or saves.

With this build you will be able to almost always do first blood. In the mid lane you will harass by using transfusion and when you are very near the enemy's turret with the champion there you will want to go next to him and do exhaust + ultimate + ignite + trasnfusion + (tides of blood if you have it available) + sanguine pool. Your enemy will die for sure and you will deal a crazy damage while being ivunerable. Pretty OP right? Also you will need to save your sanguine pool for either coming back from tower dive without taking damage, being able to dodge ganks or other ultimates like ashes, karthus, ezreals, etc. I hope you enjoyed and see you on the fields of justice!