As I've been playing with this build, I've noticed that it's more of a mid/late game build. You should play carefully in the beginning of the game and not dive anyone unless you're sure you can get the kill. Personally, I prefer building Deathfire Grasp because of its AP, cooldown reduction and its ability, which is quite useful. I've found that building Rylai's Crystal Scepter really helps with surviving and chasing down targets because of its health boost and its slowing passive. Statikk Shiv is preferable because of its attack speed and its passive which deals jumping magic damage. Liandry's Torment is very, very useful when using the Toxic Mushrooms and the Blinding Dart because its ability damage doubles when the target is slowed. Having it for Blinding Dart provides great harass with Teemo's Toxic Shot. The reason why I build Lich Bane is because when you chain it with an ability like Blinding Dart or Move Quick, it can be incredibly deadly. This along with Toxic Shot and Liandry's Torment can take away the opponents health by massive chunks. Just a word of advice, while building, it's helpful to always have one or two health or mana pods on you whenever possible, because when you run out of mana, running away is a very long and dangerous process.