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.
I've been playing Ezreal for a few months now, and he's always been my main character. I've got through a few different builds, starting out from him being my first character during a free week, and I got him the week after. I was completely clueless to a build from the start, but I've now cycled through four or five main builds, and I've found this one to be the most powerful because it doesn't require stacking items for me, and its not hard to do damage and kill once you get the first two items. My problem before was after Manamune/swiftness boots, then I'd go for something that would cost way too much, and not have good AS or LS.
This guide mostly focuses on an AS/AD Ezreal.
To start out, you're going to push for a lot of last hits. Taking arcane shift at level 2 just lets you get away, its like a free flash. Depending on the champion I'm against, and their items, I'll either try and harass, or farm. Usually champions with a Doran's something are hard to take down because of their health. If they are squishy regardless and not hiding behind minions, they're simple to damage down to near death. Armor Penetration really shines at this low level because it takes them practically down to 0. Meanwhile, you need to farm with mystic shot. Usually I get mid, and its easy to, but having a flux of damage in a two player lane can seriously damage my farming.
USE Sword of the Divine's passive. I can't stress this enough, it lets you hit massive on tanks, and lets you beat out any of their dodge and a good bit of their armor. Plus, it has a really short CD, lasts for quite a while, and you can use it maybe even twice during a teamfight.
I usually define mid game as around level 8, after your ult is up and hopefully you can snipe with your ult somewhere bot or top. Getting Manamune, or at least Tear of the Goddess should be letting you spam spells like few other champions can, and its also letting you push back your ult to try and snipe other lanes even more. I find ganking to depend highly on how well your team is doing. You should have Manamune and your choice of boots by now(I've been thinking about going for the new ionian boots, seeing as how I don't have any CDR on any of my other items.)
Also, at this point you should be picking up Vampiric Scepter for Stark's fervor. This allows you to jungle without a problem. So, if your lane is slow and you'd have to overextend, just farm some in the jungle, assuming you don't have a jungler that will get angry at you.
By now, you should be a great help to your team whenever they get into battle. When at all possible, hit your teammates with your essence flux. Its not just a buff for them, its a buff for you. The more you hit with the shot, the more it buffs you because of the passive, so use it.
At this point you can comfortably long range spam mystic shot and essence flux continually. If your teams are in a standoff, that's the way to go. Otherwise, you should have stark's fervor and be close to finishing your trinity force. Trinity lets you really hit hard, but I find that without the items before it, its just not worth the heavy pricetag because it slows you down so much to get up there.
I know a lot of people probably won't like my items very much, but I find that they work excellently in sequence because of the smooth boost in power over time, and you have enough power to gank, and to get enough power, you don't have to have 4000 Gold(My personal issue with getting trinity force within the first three items.)
I've heard some people say that you should be able to manage Ez's mana better, and there are better items than this. Yet, to keep up the spam, you need this. Going for any other mana item, which you'd need just as much for another build is less efficient. This gives you a good amount of AD(Around 50 when you've got stuff), and lets you spam your skills for about three minutes straight. I say its worth it.
This is where you just have to go with what you want. I like my boots of swiftness for chasing, fleeing, and general movement to other places. Some people like other things. I don't recommend Berserker's grieves because 25% AS isn't that great, considering you get so much through Sword of the Divine and your other items.
Third, Stark's Fervor.
What can I say, I love this item. I didn't realize how good it was until I was just messing around in a game, and I actually read how much power it gives to your teammates and yourself. Plus, a debuff on the other team(unless that got nerfed) is just plain amazing.
Fourth, Sword of the Divine.
This item gives you the insane attack speed needed for Ezreal. Plus, the active is just amazing when you're trying to kill a dodge tank or someone with a lot of armor. USE Sword of the Divine's passive. Also, it's Cooldown is super short.
Fifth, Trinity Force.
Yeah, the classic damage item. 150% damage increase after a spell cast, which mystic shot counts as, and also good stats all around.
Lastly, Whatever you want.
Really, this is where you kind of have to see what the other team is doing, and maybe get some armor, magic resist, or if you want more pure AD and LS, then go for madred's.
In teamfights, try and maintain as low a profile as possible, and try and pick off their squishies. With stark's fervor, you'll benefit your team greatly by giving them a way to get life back without having items for LS, and just generally give some health that may turn the tide of the battle.
Use essence flux in your team battles. It'll hit the enemy, it'll hit your team. It can hurt other AS characters terribly, and give your team a little uhpm.
Also, using your ult when you can hit 4-5 of them is amazing. It'll smash a lot of damage onto them, and put you at full stacks of your passive(assuming minions are around).
I don't think a lot of people would go with my summoner skills either, but I like them. I find too often that I'm dead anyways if I use flash, and I can auto attack easier than use ignite or anything else. Exhaust is another good option, but I personally like my extra mana for my lane farming and helping teammates, and teleport allows quick ganks.