Ezreal

Ezreal is strong because of his high mobility due to his E spell (arcane shift) wich is basicly a flash with low cooldown, additional damage (closest enemy, doesnt prioritize champions!) but comes with a mana cost. The diffrence between Ezreal and a lot of other AD carry's is that ezreal is skill reliant so if you often miss skill shots i recommend practicing alot with him.

Ezreal is a champion wich u need practice before you get "skilled" with him. so if ur playing him for the first time i recommend to try him out first.

This Build:

This build is made for Late game strenght and note that this is how i personally build ezreal and this isnt the only way he can be build nor is it the best build its just the best build that fits me. Im an AD carry who farms early game i dont focus to much on getting kills unless they make a mistake and this is the moment i know really good how to switch to full offensive.

Runes:

Quintessences: Lifesteal 3x

1 of the most interresting utility stats for adc; Lifesteal
I personaly love lifesteal becomes simply it makes you defensive (heal) whilest damaging your target.
although ezreal is skill reliant these runes are for my adc overall and thus lifesteal is my first option and gives you an "edge when fighting with low mana.

Marks and Seal's: (flat) Attack damage 9x

I take flate attack damage because my items are build for late game why is that?
Well its actually pretty simple if you take scaling attack damage runes u are basicly unstoppable in late game but it makes you (really) weak early game and this will make it harder, so to give myself some early game strength i take flat attack damage marks AND seals.

Glyphs: Attack speed 9x

I take attack speed glyphs because im offensive as can and i need the early game flat attack speed to keep up early game and due to the items im strong enough late game.
also i take these because i dont really build any attack speed items like phantom dancer because ezreals passive grants him more then enough attack speed together with Trinity force.