Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This Build Will Own Any Champion, Anytime, Anywhere. If you are facing a team with stuns and slows, I would suggest getting Mercury Treads, No matter what champion you are playing. If played smart, you can easily 1v2, and you are a great asset to your team. You should always come out positive with this build, and in most cases be the team carry.
I don't depend too much on Ezreal's Ult, I mainly use it when initiating a teamfight. Using his Ult at the start of a teamfight is a Great way to hit most enemy champions as well as give your team an advantage by taking a little chunk of their health.
I use Mystic shot mainly to harass/annoy the enemy champs. Because of it's Short cooldown you can really do a decent amount of damage to someone from a good distance. This skill gets stronger when you acquire more attack power, and also applies on-hit effects. Which is why Phage/Trinity force works so great for this skill.
I Max out arcane shift first mainly to use as an escape spell. Also, When attacking someone, it does great amount of damage to an enemy champion while throwing them off a little.
Essence Flux is just used as a support spell in this build, only used to increase ally attack speed.