First u make doran ring, and choose Q skill - Star Call.

if you can beat enemy or dominate mid u can choose second skill E to silent him.

If u have hard mid land you can Choose W to heal yourself. Doran Ring provides you enough mana to use Q to gain constant farm.

Q skill - Stal Call provides enemy's reduce magic resist stacked to ten times !
When u build Lich Bane as the second or third item after boots and Doran Ring the reduced enemy's m.res and your normal attack from Lich bane with Q will perfectly damage enemy

Without second and third Doran Ring you have to take Blue

To gain Perfect farm just spam Q skill and remember to wait a little to kill last hits minions.

if enemy approaches, let him get closer end use E - silent with constant Q

with 2 or 3 Doran Rings a don't have to back to regen mana or heal. 2 or 3 dorans provide mana. 10 or 15 per minion and you have heal of course.

Long range normal attack with Lich Bane are perfect compilation for harass.

when u build fundamental items which are: doran, magic boots and Lich bane and you beat enemy's tower on mid u can help other teammates on bot or top with heal and mana regen or silent enemy.