I love play Ezreal like AP because all his skill are going to AP and it's not hard to learn AP Ezreal.
I use RED for stronger skill's in early game,YELLOW are standard and I use BLUE for stronger skill's like RED.It's great combination of RED and BLUE.
I use 9/0/21 masteries because Ezreal in early game need Mana and Mana regeneration.I put 9 in offense for AP and cooldown.
You will need Doran's Ring because it give Heal,AP and mana regeneration.I choose that shoes beacue Ezreal need some Magic pen. for stronger skill's,Rod of Ages to not be ''squishy'', Rabadon Deathcap for good AP,Rylai's Cristal Scepter for some HP and Void Staff for end game when all will have some better magic resist.
Essence Flux is the 1st skill because it't the most stronger of all.2nd Mystic shot and now u ask why 2nd Mystick shot?Hmm...2nd Mystick Shot because he use a little bit of AP,that skill is for AD Ezreal.Arcane Shift use just for teleport,and Trueshot Barrage you can use it from your base to farm a minion or to kill enemy.
I use Ignite when enemy is on low hp and Flash to have 2 teleports.So if enemy chasing you there is no chance to kill you because you can cast 2 teleports.You can cast teleport through
Ezreal can cast spell's through wall,always stand behind minions and when you think you are redy 1st teleport to enemy with Acrane Shif then use Essence Flux and Mystick Shot and drop ignite on enemy.If u think that u will fail just flash back go to turrent and hit enemy with Trueshot Barrage.