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.
Starting from the way you get your skills, i can tell that mustic shot is the important 1 here. BUT. choose second the essence fluc. Why? maybe arcane is more damage but, essence will make you have 1 more skill to burst and is also a clear shot to push or assist even beside mobs. You will often need to have a shot like this, cause ezreal skills dont overcome mobs. Also, as you advance in lvl, this will not be your most important shot but will help you to burst better with one more shot, as i told you, even while mobs in front of you and this will quite often happens when you push to towers and want your enemies to recall. So, remind to put some skills in essence as well.
I will explain the mecanics of this set up. First of all with ezreal you need to spam your mystic shot. Starting in lane you will have the option, by aquaring mark pendadt, to loose some shots but using your mustic shot quite often. More than this, cause you probably do midle lane, you will have the heal to push or risk to kill your oponent. with teleport you will not loose time to take some items for you. Some ppl advice flash. I m not on it. most of it, cause you will see that with ezreal your first escape choise will be your 3 skill. so, most of the times flash will be unused. So, teleport will be a wise choise anuway and heal will help you survive a lot of times. specialy in starting lane.
Now, ezreal is one of the best carry dps. Your runes are giving you penetration and you can use your mustic shot often, that will be enough for the start. Since ezreal is 1 of the best carry dps, taking sword of the occult its not a risk. you will not need shoes in lane, since you have more speed from your skill tree and furthermore, you have big range with skills and unranged ulti. you are not chasing in lane big distances, so, taking the occult sword fast and coming back with teleport will help you build up your damage. More, the 1300g is an amount you can easy get.
As the game advance's you find out you have to spam your abilities so you can use your ulti more often. This is a key. having your ulti most of the time open will be crucial. So, build up your mark pendand to Tear of godness. This will be fair enough and will not make you going back to base all the time. also, you can push and risk shots withoug thinking mana. More on this, you can later build it to manamune and this will give you some more damage with your maximum mana growned.
After that, the game will include probably some team batles. So, now you will need more dps. Chose up your sword starting with BF. I m suggesting Infinite edge cause is the best. But if you dont have enough money, you can pick another one.
You will find out that your dps is fair enough and you now need more spam. Brutalizer will help you with this. Also, you can later build it to ghostblade. And after that pick up some more dps or if you find out your oponents leting you nuke them from close distances chose seen, which also can build up.
They key to all this is that you can take items in the correct timing that the will help you the most for the period of the game you are and you can later build them up. So, your first choise, occult sword is fast and sure is helpfull cause even if you dont do kills you will steal up a lot or assist with ulti. Also you are Ezreal, so, you are anuway an op dps. You are not ryze, so, you are more hard to kill. When the game is heading for midle game, having mana to spam mystic shot will be very importand. Thats why i m suggesting the build in tear of g. This will also let you have your ulti very very often, and your ulti will help you improving with assists or kills the stacks in the occult sword. Also, you will build in it manamune when you decide to. The rest are know. You will have to decide your swords and going to heavy dps but also having very often your ulti.