Not Updated For Current Season
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