Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Start off with boots to make lasthitting minions with Q easier and then retreating back to safety. (Turn them into sorcs boots later, your R is magic dmg, more dmg on it means it heals more, with this build you can return to full health by hitting a creepwave with it. Works on champions too of course.)
Depending if other team has a jungler or not get sightward(jungler) and 1x health pot and rush to their blue and ward it, or 3x health pot(no jungler).
Your Q and your R are your main dmg sources.
use W just before engaging with Q then slow target with E and start spamming R while continuing to hit it.
Now to the optional part.
You have 3 choices for your situational item.
Depending on what the enemy team is doing.
If you happen to become the carry and enemy team is starting to stack armor (or for some other reason), get a last whisper. Watch out for players with thornmails. It can drain your health faster then you can lifesteal sometimes when focused.
If enemy team has many DPS or one heavy physical DPS that is giving you troubles, get a thornmail.
If youre lucky and the enemy team doesnt have a phys dmg carry, get a banshees veil. It gives additional health, nice MR and the lovely "no spell 4 u" bubble.
At around lvl 3 your W+Q combo can already deal some nice dmg.
This build is best played in Lane with a champion that can harras enemy champions to half health or with someone that has a stun.