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.
Glyph of Clarity to support her low mana. Seal of Vitality to give her some more survivability. Desolation Marks/Quintessence to really punish players early game and paired with Last Whisper keep her active late game versus heavily armored targets.
Zerkers Greaves early game for help escaping and increasing headshot procs. Last Whisper is next to give you an early damage boost and increase punishment through any armor items opponents may have upgraded with. Bloodthirster or Phantom dancer is next, depending on if you need lifesteal to keep yourself alive or you want to go for faster movement and crit to help with ganks.
Next up is frozen mallet to keep enemies from getting away in the event they miss your net or yordle traps, as well as help you withstand a bit more damage.
Finish it off with Infinity Edge for the increased damage