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.
Only truly viable gp build. Forget what you know about triple avarice.
Built so you have a steady A/S with RM, balanced out with mediocre AD and then decent crit rating mid game, and amazing 5 second nukes in late game. Make sure when you built youmuu that it is binded to a convinient hot-key for use.
Do not built meki pendants early game, allow the recommended glyphs and seals take care of your mana worries. Start with boots and 3 health pots. You are a viable mid player, call it if you want. Getting fed early game is the key to your extremely broken critical calculations in late game.
Use your cannon wisely, farm a minion wave or two if you have the spare mana and CD. But more or less, try to save your towers or allow your team to push. Cannon can also be used to force a team fight and is a very viable mid-game push skill.