This build is a lot of fun.

I prefer getting the Mejai's Soulstealer every game unless I am doing really bad, because your Trueshot Barrage You're going to automatically get stacks on your Mejai's Soulstealer. But since snowball items such as the Mejai's can be a dangerous burden later game, i get Zhonya's Hourglass to preserve my stacks and just to piss people off is another reason you could

Ezreal has early game mana problems so i prefer putting points into the mana masteries to counter this.

Farming: since your Mystic Shot does not take much mana i would suggest that you use to to last hit without getting harassed, i've found this very useful