You can either get W or Q level 2. W will protect you against poke, Q will let you poke. Just look at what you're against and pick one.
Corrupting Potion:
We are planning on early recalling to buy a Doran's Ring, so this is a great item to play fast, stay healthy, and clear the wave when we need to do it. You get more and more value out of this item whenever you recall.
Doran's Ring:
Recalling with the intention of buying a second starting item Doran's Ring might sound odd, but it really helps out your laning and it is a really efficient buy. You can clear caster minions with 2 Qs after you recall early and buy Doran's Ring
Sorcerer's Shoes:
I would try to build this as my default boots. Don't build others unless you have no other choice.
HEXTECH rocketbelt or Night Harvester
They fill a similar role. Both are good items for sticking onto a target. Just try them both put and see what you prefer.
Rabadon's Deathcap and Shadowflame:
They fill similar roles. They just deal damage and are better if you don't need magic pen.
Void staff
If they have magic resist, build this.
Nashor's Tooth and Lich Bane:
These items used to be better, but after the rework, it isn't as appealing. Nashor is pretty much only decent in a Conqueror Build.
Oblivion Orb:
Cuts healing. You are a burst champion though so you often don't need it. Burst counters healing... because they are dead.
