Hey, this is my first build and i am lost.
I think you guys will like.
I am from Brasil and my English isn't perfect. Sorry.

Start with a Long Sword and 2 pots, in the early game you don't need boots with ezreal mobility.
After the first time you go back, you should be able to get a Vampiric Scepter, a Berserker's Greaves and a Crystalline Flask. Then you rush a Bloodthirster and a Statikk Shiv (that it will help you a lot to farm). When you get stronger you get a Infinity Edge or if the enemies are with a lot of armor you should get a Last Whisper first. After you get your Last Whisper, your Infinity Edge and your Guardian Angel you should sell your Berserker's Greaves and buy a Phantom Dancer if the game does not end. And to end you should sell your Statikk Shiv and buy a Trinity Force.

I like defensive summoner spells but you can change barrier by ignite or cleanse if you are playing against a support fiddle.

Ezreal has unique mobility with his (E) and his ult (R) can be used to snipe enemies, farming pushed lanes and a and to do a lot of damage in team fights. His passive can be used to destroy turret very fast, you just spam your abilities and hit the tower with the attack speed you gain with your passive.

Stay behind, use your (Q), (W), (R) and auto attacks. (E) to run and try not to die.