I've been playing Ezreal regularly for about 2 years now. I wouldn't say that Ezreal has any specific or challenging mechanics to learn. All of his Abilities are skill-shots, so they do require a fair amount of practise. I agree with you, however, that you should learn the Range and Damage outputs of Ezreal's abilities almost of-by-heart before being confident enough to dive in to a fight and come out on top. But then again that's the same with almost any Champion. Just be careful when using Arcane Shift [E] in the jungle, or in lane, as it does not prioritise Champions and may attack a Neutral Monster or a Creep, and reduce the amount of damage you do.
There aren't any Combo's or Attack sequences. A Mystic Shot [Q] then Essence Flux [E] is how you get most of your damage. It will be good to shoot both of them off really quickly. What I do, is I have Quick Cast turned on. This means that I don't have to click my mouse to use an ability, I only have to press the ability key on my keyboard. This does however mean that you can't see the Blue Hit Box which Shows up when you hold down they key. What I would Recommend, is having Semi-Quick Cast turned on. This uses an ability when you release the key on your keyboard, or press another ability on your keyboard. It's a lot nicer for beginners as it gives you the best of both worlds. You can find these setting in the Game tab while In Game.
Hope this helps.