Only way to play Ezreal is blue Ezreal because trinity force + crit Ezreal is for pussy ass bitches that can't land skillshots. Whenever blue Ezreal is not viable in the meta, never play Ezreal because Lucian does his job better whenever Ezreal cannot function as a poke champion; that's why Ezreal was shite during the tank meta.
And muramana dumb? It's like the best item on Ezreal; gives you 1000 mana, the mana refund, gives you around 70+ ad and adds 100+ damage to your Q, E and auto attacks.
Manamune > Iceborn Gauntlet > Blade of the Ruined King > Lord Dominik's > whatever, is the normal build path.
All you need to learn to get good with Ezreal is land your Qs; after laning phase, never get into auto attack range of anyone, even the enemy ADC, just keep poking with your Q and E in whenever you see someone you can kill. Ezreal can delete squishies with around 50-70% health and can 100-0 them if he uses ult so don't be afraid.
For Orianna? I don't know about Orianna, Orianna is for pussies that just like playing supportive mid laners. I ain't into those kind of champions.