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.
i like to start off with dorans ring and a life potion. You wont need a mana potion because you have Clarity that will restore your mana for you if need be. then later in the game i trade Doran's ring for Zhonya's Ring for more ability power
but before i get Zhonya's Ring i buy the less expensive stuff first.
Starting with Soul Shroud
and then Innervating Locket
and this is your choice but i would by Lich bane before the archangle's staff only because of the movement speed combined with ability power. But depending on the situation i would get boots first then trade it with the lich bane later in the game.
Why so many boots?
well i choose the boot depending on who im fighting against.
like when i'm fighting DPSr heavy team i get Ninja Tabi for its dodge and movement speed
When i'm figint against a team that is magic heavy i go with Mercury's Treads
and just for a general fight where its like balanced, i would get boots of swiftness
Then later in the game buy Lich Bane and trade the boots in for it.
Then i personally would get Archangel's staff later. I get two because the ability power.
This build has done a lot for me and i hope it'll do the same for you :)
GL and HF <3