I find your item choice lacking. I agree with your choice of Lich Bane, as this is AP Ezreal's core item. Rabadon's is pretty standard on most AP champs, so this is a good choice as well. Ionian boots of Lucidity are a good call, too.

Your build has a lot of Magic Resistance and a lot of Magic Penetration/Magic Resistance Removal. I find this unnecessary in most normal games (you stated in the guide that you rarely use this in ranked), as very few players in normal games will stack magic resist, with the exception of tanks.

Morello's Evil Tome is a decent choice, though if you remember to use actives then Deathfire Grasp is slightly better. I tend to use morello's myself, though I see the advantages of DFG.

The Void Staff and Abyssal Scepter seem unnecessary unless building situationally against a magic resist stacking team. Besides, with lich bane, your Q essentially deals PHYSICAL damage with a 1.2 ratio (0.2 natural ap ratio plus it procs Lich Bane's effect on cast and consumes it on hit). Your biggest nuke will deal physical damage, despite building AP. I prefer Archangel's Staff, as Ez can build it easily using his spammable skills. It gives him a massive mana pool, good regen, and synergizes with the mana from Lich Bane to give a spammable skillshot champ lots of ammo to work with.

Another item to consider is Rod of Ages. It gives him some durability, sustain, power, and even more mana to synergize with Archangel's.

My standard build is this:
Ionian Boots of Lucidity
Archangel's Staff
Lich Bane
Rabadon's Deathcap
Rod of Ages
Morello's Evil Tome

Nice first guide!I have 2 from my own!(Check them if you want :P)I may try AP Ezreal!Continue with the good work!