Ezreal is a very safe pick for an adc . He is best at poking down opponents and can make very big plays with his kit . It takes a while to master Ezreal but a great Ezreal player can almost always win lane .

If the game drags on long enough it is a safe option to sell your boots and buy a guardian angel as that helps in team fights .

As an adc you want to be constantly farming the whole entire game so that you can have the most available items , however do not stay in lanes for long periods of time pushed up alone withou vision as that makes you very prone to gankss

Ezreal's ultimate is very good for team fighting , its best to use when a team mate uses an aoe slow or stun so you can hit as many people as you can . You also want to make sure to b e working with your front line( Tanks) and make sure your kiting

Ezreal is a very safe picked for ranked since he basically has a flash on a 10 second cooldown which makes him a very hard target to kill in early ganks , however you should not pick ezreal if the enemy team has a draven because draven destroys ezreal in lane