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.
Annie, the fastest flame, is conciebed to be an interception champion who can burst to death any enemy, with or without help, depending on the situation.
Boots, Quickness (mastery) and Lich Bane make her one of the fastests casters you can encounter, with the additional possibility of using Ghost to catch your enemy and reduce him to ashes.
(About the items: First of all, we need the most expensive item, Rabadon's Deathcap. The 30% bonus on AP will make our victory in every item we purchase. We alternate its purchase with the boots. When you have both, it is time to reduce the Magic Resistance of our enemies with the Void Staff (remember that every single champion have 30 MR base). After this, Lich Bane gives us the ultimate speed of our champion, getting 80 AP on the way (more, if we count with the Rabadon's). Fifth, we take Abyssal Scepter to reduce even more the MR of the enemy, and the Rilay's Scepter in order to slow them (as an extra to our speed).