Well, Ezreal is definitely one of my favorite ADCs. You can however, play him as a AP Caster in the middle lane. Playing him middle lane is extremely fun with all his quick abilities and short cooldowns (not to mention nearly 1 shot'ing people with his ult). For me personally I think that Ezreal is stronger as a champion in the bottom lane. Many will agree with this statement.
Here are some builds that are strong...
_AP Ezreal: _
Build 1: Complete Glass Cannon

_AD Ezreal: _
Build 1: Blue Build Ezreal
(You can swap out
or
or for other items as well. An example would be
)
Build 2: Basic ADC
(You can swap out Bloodthirster for
. As well as swap out
for another offensive or defensive item)
Build 3: 40% CDR Ezreal
(Once again,
for another offensive or defensive item. To achieve 40%, you need to run some extra CDR either in your masteries or your runes)
Build 4: Build Fit for Ezreal
(Once again, you can swap out
for another offensive or defensive item. You can also swap out
for
depending on what you prefer, the attack speed or cooldown reduction)
There are some pretty good builds to use when playing Ezreal.
Generally it's fairly difficult to be extremely aggresive in lane like a Kalista or Caitlyn would when you're playing as Ezreal. Ezreal's laning phase is not the strongest, however, it's not the weakest. You rely a lot of your Q which is difficult at time to land when you're in lane with all the minions in the way. He is is extremely strong mid to late game. He hits a huge powerspike when he gains his
or
depending on what you're building. He is very hard to catch and lock down during teamfights because of his mobility, making him an easy ADC to learn. However, all of his abilities (except for his E) are skillshots. Mastering landing these skills will be vital to your success.
Anyways, that's all I have to say. Have a good day and I hope to see you on the rift.
~Spheres