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.
Fairly simple build for a carry ez in a 5v5 mid. ArP/Mana regen to keep the damage high and, well, without mana ezreal is useless.
grab dorans ring or blade at beginning, depending on how dominant you are in lane either pick up your BF sword or grab boots then rush bloodthirster. afterwards pick up a sheen because it will improve your mystic shot and arcane shift. grab boots of swiftness because you don't need attack speed due to your passive. at this point you'll want a slow, so either pick up a phage and work on trinity force after black cleaver, or turn your phage into frozen mallet for the health, damage and slow. your last item is optional, i prefer another bloodthirster for the insane damage you have at this point.