At first take "w", you can use it very often, but it cost much mana, so sometimes try to save it. It deals nice damage with Arcane Comet, so try to use it on minions and enemy at the same time. Try to get as much gold as you can get, becouse you need to scale up quickly. After buying lost chapter or completed echo, you can use your "w" much more often, becouse mana should be not a problem for you (with Manaflow Band). When your stopwatch is ready to use, or you have already bought Zhonya, try to get as much as possible enemys on "r", and when you will get focused, use it. Morg is really satisfying thanks to this combo. Good luck, But please, play some normals before you start playing Rankeds ;)
Have a nice day