You should have your basic GCD rotation unlocked by Sastasha, and you should have all of your abilities by level 50. That gives you 20 levels to practice them before reaching end-game, and will let us use all of our abilities in everything but leveling roulette.

Regularly unlocking abilities as you level up has never made leveling more fun or engaging to me. Most of the time it just leaves you with an incomplete and awkward toolkit until you reach a certain milestone.