Blue ezreal the upgraded version

There are cons of this build, but they are mostly ezreal issues in general like you are mediocre in the beginning, weak before 6 and you are only good around 15min mark and onward, if you get behind its not easy to get back and so on.
But this build emphasizes the parts in which ezreal as an adc excels at and amplifies them.

CONS

Mediocre early game
weak vs caitlyn
requires high knowledge about blue ezreal gameplay

PROS

High mobility
40% cdr
excellent kiting
Huge mana pool
armor penetration
high attack speed
%dmg on hit
aoe cc
defensive stats

THE REASONS FOR THESE RUNES

You don't need to go cdr per level cause you get 40$ cdr from items.
You will go as blues and you will dodge all the enemie midlaners skill shots and blame yourself if you don't dodge and lose because of it. Ya boosted animal
Hybrid pens give more damage value around 15min mark and onward.
There is no important reason why i go 1 lifesteal quint, you don't have to if you don't want to but i think its good.

ayy lmao

18/12/0 is the standard and it is really good, if you are an experienced ezreal player i would suggest you go 18/12/0, but if you are familiar with the ezreal playstyle if you so choose to go this build i would suggest you go 18/0/12, its not as bad as it seems, sure you sacrifice 5% heal after a champion kill and 5% dmg increase and savagery helps with early game cs'ing cause you are lacking ad in first levels, but in return you gain incredible sustain synergy with healing/shielding supports[heal supports and shield supports are meta now] and most importantly utility!
UTILITY is BETTER THAN RAW DMG because with utility you will land more q's and be able to dodge and kite and land even more q's.

So you think that trinity and gountlet don't stack? Yes and no. Sheen, trinity force ,icebourn gountlet and lich bane all have the same "unique passive" but if you build these items together lich banes active will be activated only but the slow and aoe dmg will be activated as well.
1) say you build trinity force icebourn gountlet and sheen.- trinity's 200% dmg will be applied, gountlets 100% dmg wont but its aoe and slow will, sheens dmg wont be applied.
(Gountlet's sheen damage is 100% of your basic ad and trinity forces sheen dmg is 200% of your basic ad.)
SO THE ONLY THING YOU LOSE IS THE 100% DMG FROM ICEBOURN FOR WHICH YOU SUBSTITUTE 200% DMG