Cho is very very mana hungry hence the clarity, it allows you to stay in lane to gain precious xp and gold. Start out just last hitting minions and using your Q to keep the enemy at bay, an early farm is crucial for this build to DOMINATE. Rush Rayli's for the slows, it will allow you to be aggressive and have escapability if things go sour.

Don't forget that Chos passive is essentially lifesteal as far as your concerned, if you are sorta low just kill some minions or neutral monsters to get health back up. Once you have any amount of AP, your Q will be able to one hit minions, so you can use it to kill a lot of them very quickly and get you a substantial health boost. This can also be a good way to bait an enemy into a fight, let them see you are low then knock up and kill a group of minons, restoring health, turning to the enemy and screaming at them to buy time for your knock up to come off cooldown, after you do that and begin attacking, it is easy to make short work of them with your spikes making it hard for an escape on their part

If you are smart with your early game play and keep your stacks up on the rare occurance you die, it is very easy to do extremely well as the game grows longer; its very hard to beat a Cho with AP in the 4 or 5 hundreds and ah health hovering right around 3000.