Ez is one of the difficult champions to choose. Only Skillshots. You like it or you hate it.
Because his abilities scale so well, i like to play him hybrid.

If you want a good AD build, try http://www.mobafire.com/league-of-legends/build/booshidos-ad-ezreal-43156 Booshido's AD Ezreal
or http://www.mobafire.com/league-of-legends/build/ezreal-ad-bar-hopping-and-pub-stomping-73170 Ezreal[AD] - Bar-hopping and Pub-stomping

Greater Mark of Desolation Greater Quintessence of Desolation : You get ArmPen on your (25 Armor Pen at the beginning, nice to have )
Greater Glyph of Replenishment : You want to spam your abilities, last hit with your is easy, to keep your mana in a safe area, i only take MP5 runes.

I wouldn´t go for . In theory you can use your abilities more often, but no mana, no skillshot. With my masteries you get 9% CDR, with the Boots, its up to 24%. Think thats enough for Ez.

1. and 2 . You can spam your more often, use it for last hits or harass enemy. You can play very defensive, let the tower hit 1 ranged minion, and finish it with .
2. Don´t go back before you can afford and . (If you are forced to go back, only take Sheen and maybe some Potion )
3. It depends on the enemy team which item you go next. or TheBloodthirster. If you miss a lot of your last hits, go for , it boosts all of your skills and 800 less then The .
4. After and , go for . Each skill of yours, slow the enemy, so you can easy get away or chase them down with an combo.
5. Remeber: , and are your core items. You want to get them in each match.

Your core items cost: 10650 ( with boots )

You want to go mid. You need to farm a lot, and your lanemate wouldn´t be happy if you kill all the creeps ( i assume that not every game someone is so kind playing a support with 0 creep kills )
Important: You can nearly get every minion under your tower. So you can play aggressive or defensive. How you like.

1. ranged minions: let them hit once by the tower, then finish of with your , or and autohit
2. melee minions: 2 hits from tower, 1 or autoattack .

Pros & Cons

Pros

perfect last hits
can spam his skills
escape for dummies ( e and flash )
fun to play

Cons

only skillshots
easy to fail
no CC ( slow after Rylai´s)
some mana issues if you dont use manareg runes.
Squishy early-mid game. ( Rylai's helps late game a bit )

Here some prove that it works quit good, if you dont mess up :D