Basically the build is this
Blade of the Ruined King
Ionian Boots of Lucidity
Spirit of the Elder Lizard
Runes can be anything
This build gives you 300 AD, about 60 AP, and you get 35% Cooldown Reduction
It allows you to spam Q every 0.5 seconds because of Ezreal's Passive.
His E is about 7 seconds on CD, and three Q's will put it back and ready.
Your Q deals about 400 damage, plus it has a 60% slow.
This is the new OP right now. Every Korean ADC is now experimenting with "Blue Ezreal"
All his items are blue, and most of them are pretty cheap.
He's weak early, but with Frozen Gauntlet and Spirit of the Elder Lizard, you should be able to feel the power of "Blue Ezreal" from then.
He can basically kit really well with Furor Enchantments, his E can be used more than 4 times in teamfights, and you can spam ult to keep lanes pushed.
How I built him
Dorans - Tear of the Goddess - Boots - Gauntlet - Spirit of the Elder Lizard - Finish however you want.
Oh and you wanna get Vampiric Sceptor just for the Life Steal
If you don't trust me, try this on Custom, playing 'Blue Ezreal' feels like your playing an FPS.