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.
Whoring It Up
This build focuses on turtling until you get Soulstealer. Once you get Soulstealer, rack up a bunch of kills to get an unhealthy ability power. From there you can basically chill in the back slamming down heavy artillery on your enemies. This build requires a friendly tank, otherwise the enemy will just charge for you.
Anyway, there's a great benefit in using stacking items with such a largely range focused character. When you can slam your enemy with 160 base + 300 ability power (460 for those who need it (you shouldn't need it)) you just don't care. You wail at your enemies all day long. The last item is so that you can regen your mana, as multiple Living Artilleries chews through that rather quickly. Be sure to hit ballsy enemies with Void Ooze. 260 dmg + 300 ap just wrecks them, and it slows them for your teammates and the following barrage of artillery. If you can get your Caustic Spittle off (you're too close) if fully upgraded it will be just as devastating as your ooze. So let's recap:
Void Ooze: 560
x3 Artillery Strikes: 1380
Caustic Spittle: 560
Total: 2500 AKA raging opponents.
Anyway, that's how I play. The games can get long sometimes but I haven't lost yet using this.