From what i've seen, most ppl play Ez as an AD carry...all fine and dandy, but that play-style just aint for me.
I got Ez first time thinking he is a mage . . .AND I WAS RIGHT. i just said looks can be deciving, didnt I? The ratios he has on his spells make him an extremly good nuker

Im not assuming you are reading this cuz you just got Ez and want to find out what his abilitys do. No, its either for those who usually play AP Ez or are making the switch from AD, so im not gonna explain the spells cuz i think you know how to
Q:-last hit minions
-chek brushes for ganks
-reduce the cooldowns on your other spells
W:-harass and nuke enemy champions
-boost the attack speed of AD champs during tower pushes
E:-escape from tight situations
-close gap while chasing
-hop over small walls
R:-Kill low fleeing enemys
-clear minion waves
-defend turrets from any distance
-Kill more enemy's

I dont recommend you do this untill u get a good grip on all of Ezreals spells range....
change your keybinding to smartcast with basic Q W E R. makes you fire off shots much faster, and u pull of combos easier

Mastery's are really self explenatory. For runes i just posted why I use and here's why:
with the mastery skills and the yellows and blues, at lvl 18 i will have 20% CoolDown Reduction[CDR], so with Morelo's extra 20% i get capped with a single cheap item

i start with a meki pendant so i can hit those mystic shots without thinking about mana at all. this will be upgraed into a tear as soon as i have the gold for it, so it starts staking ASAP.

next should be the boots, cuz we need mobilty, dont we?

after that i get a Fiendish codex, this ensures my mana regen and gives some nice CDR and will later be upgraded to Morelo to max out the CDR

Like any good mage, I get Rabadon next, huuge boost to my AP

Now's the time to finnaly upgrade taht well stacked Tear into an Archangel staff and proly be a good ideea to upgrade the morelo as well

Now if the game still lingers on, Rylai's Scepter is always a good choice for any mage. This is my favorite item on most Mages and Hybrids. it gives good AP, Good HP and the slow on it is pretty cool
Last item should probably be a defensive item of your choice, depending on the enemy team

I pretty much always go mid when i play AP Ez and i suggest you do the same. I take TELEPORT and FLASH for my summoner spells. i like to get as fast as possible from shop to lane and not waste time walking. The flash u may say its not needed since Ez has a built in one, but what he has is very mana hungry early game and its range is very short as well. also with both flash and arcane shift im extremly hard to kill and thats a very good thing and you should want it too. if you dont like the TELEPORT, take whatever you are used to...maybe IGNITE for those pesky cowards or healers, or EXHAUST for the greate chasing power, or even GHOST, that way you'l be Extremly hard to kill.

From lvl 1, stay safe, far and only last hit minions with Mystic shot. Dont even bother harrasing under lvl 5 unless u get an oportunity for some free hits on your enemy.
So start with Q for lasthiting, than E for the mobility, just in cae, than u put points in W every chance your get, cuz that will be your Harass tool, your main damage output early on...[on champions, dont forget]
Once you hit lvl 6 and get your ulti u can look on the map for some half-dead enemys you could snipe. Dont be afraid to miss, cuz you will....alot. remember your have high CDR and another cool tool: your Q lowers the CD on all your spells every time you hit something with it, so spam the **** out of that thing every time u get. This skill will help you fire of ultis at insane rate, between 30-40 seconds sometimes, so i say again, dont be afraid to miss woth R, or even clear minion waves