Walk/Flash into fight. Press Q. Press W. Press E. Press R. Press 1. Win game. Sustain forever. Please learn to play Morgana...
Tldr: Morgana is useful because of her CC (which can screw entire teams over), not because of her damage.
But if you want to let your entire team win? Go starting item (dorans/boots/mana crystal+mana pots), then build rod of ages, Rabadons, Zhonyas (Flash into enemy team, Ulti, Zhonyas when they try to focus you, stun them all, you've just won the team fight. Note: you can activate Zhonya right after you hit R, because its not a channel spell and won't get interrupted), and then situational items (ex: magic penetration, banshee's veil, DFG, etc). Also, push mid (almost nobody can beat you in mid cuz of your sustain), and then go gank
Really nice detailed info, but I dont get a few things:
a) Why not dorans ring? Just because you start with good AP already doesnt make Dorans bad. A sapphire gives 200 mana, whereas a Doran gives you 60 mana per minute, plus the AP and health.
The only advantage of Sapphire is if you need the 2 health pots. With her extreme range and built in vamp, I would think she wouldn't have as much need for them.
It does get your Catalyst earlier though.