This ChoCho focuses on speed, damage, and crits, so all the attack specs in there can help him.
Rupture and Vorpal Spikes are chosen first because the rupture knocks enemies up which is very helpful for supporting your lane partner while they make a getaway and slows down the enemies running away from you, and letting you have the time to land so hits with your strong Vorpals and then landing a feast for the NomNom bonus. Feral scream is last because it's not a necessity beginning game for this build.
Exhaust and Ignite are possibly the 2 most OP spells there are, Exhaust reduces the damage output to just 10's of damage for those head on fights you need to survive so you don't lose a spree or you need that 300gp for your build or to slow down those sneaky bastards who don't get hit by your rupture, it' basically a no survival spell. I choose ignite because there is always someone who is lucky enough to make it out alive with just a few points of HP left, Ignite is here to change that.
Phantom Dancer x2, you need attack speed, the crits are very helpful, and you move faster to catch up with you enemies.
Bloodthirster, IDK why but its very good to have it, he regains hp like a madman early game when your just at your Zeal and Vampiric Scepter.
Boots of Swiftness, No reason not to...
Stark's Fervor, again, you need attack speed and extra lifesteal can't hurt, the buff for allies is very helpful as is the debuff to enemies.
Sunfire Cape. Keep in mind you're not invincible, and the more hp the longer you live.
Exact Item Sequence
Dagger-HP Pot-Zeal-Vampiric Scepter-Cloak of Agility-Phantom Dancer-Dagger-Zeal-Cloak of Agility-Phantom Dancer-B.F. Sword-The Bloodthirster-Boots of Speed-Vampiric Scepter-Recurve Bow-Emblem of Valour-Stark's Fervor-Giant's Belt-Sunfire Cape-Boots of Swiftness.
Hope this is extremely helpful to all of you people who want a new way to play this awesome champion! See you o on my n ext b uild! Byeeee :3.