ADC champs have a lot of possibilities. This build has helped me be able to get into team fights and back out quick and clean. Maxed cd insures that you can keep throwing skill shots and also have your e to escape if needed. Sniping with your r happens much more frequently as well.

Basic runes, as comes from Ezreals passive no need for runes.

High Ability damage, your q is going to be your best friend. meant to build damage and snowball enemys with abilities Fervor stacks with all of ezreals abilities making his basics significantly stronger.

Building Trinity Force requires a decent amount of patience and practice. Landing your Q will garner you the most damage and missing it can be deadly. The increased movement speed and damage is very helpful when it comes to jumping in getting a few shots and jumping back out. Keeping in mind that you are going to be squishy as a dazy underneath sions boot remember, no risk no reward. Ghoste blade and Muramana can be switched around based on how you are doing and if your tear is getting close to done. Essence Reaver subbing in for boots can do a couple different things. More damage while keeping the 10% cooldown, 20% crit chance and restoring mana on crit are very helpful for long engages and late game. your Lifesteal will sustain you if you need to back and take out some critters or jungle monsters while your team revives.
Keep in mind Lifesteal does not mean they will do less damage, just you will gain some health on your q and basic attack. getting stunned or rooted out of range makes it hard to heal and the 90 sec Cd on Mercurial Schimitar makes it hard to take on enemys. Ezreal will never be a 1v5 ace type champ but he can get in and out pretty easy, and sustaining yourself and defending is much easier by your self if you can evade the enemy teams stuns or negate them.

Your Q is your best friend, aiming it well and landing your pokes is the key to winning lane phase. W doesn't scale off of ad so keep its use to a minimum. I mostly use it just to get another stack of Fervor and in team fights increase my teams AS. Your E will help you engage and disengage. don't be afraid to use it to reposition during lane phase to poke or get cs. Ezreals ult losses damage to a certain point the more enemys it hits. avoid using it to clear waves as it won't be able to kill all off them. Also while sniping enemys try to avoid jungle camps.

Flash and Heal help get you out and or secure kills.

Use your Q to build your Tear at first, be sure to keep enough mana for surprise ganks or bad engages, we all have them.

It is very difficult to Steal Drags and the Baron with your ult, save it for clean up duty or poking before team fights. Communicate with your team and try to use it once the fight starts aiming for the enemy ADC, Assassin, Mage, Then Healers and tanks. Your W gives AS to any ally it hits including ezreal, try to hit your team with it as much as possible especially while on baron or drags.

Play smart, know your cooldowns and distances your abilities will go, it is easy for Ezreal to get surprise kills just because someone overstays their welcome. This build is made to have quick games, the difference between a win and a lose is how you play, and who you play against.