This is a Morgana build I use and it has never failed. Tons of mana, Lots of spell vamp, and tons of AP. What's not to love?

Starting of at level 1 with Dark Binding for all your bottom grass ganking. Grabing 2 levels in tormented soil to start doing damage to minions. Another Dark Binding cause usually the sheild isn't needed right now.(If it's needed go for it) Level 5 we click the plus sign above Tormented Soil(Rank 3 Soil is enough to kill the back row of minions) Getting Soul Shackle cause, duh. Now max out Dark Binding, this will be your biggest damage output. Pick up Black Shield at 10, then followed by Soul Shackle at 11. Max out Soil, then max out Black Sheild. Then be the best support ever.

Straight ability power. You need more ability power in the beginning with this build

First the basic Doran's ring, needed for any mage. Tears of The Goddess for that extra mana. A little late with Sorcerer's Boots, to maximize the effectiveness of Tears of The Goddess. Then start building your pretty little self a Will of The Ancients, stacking spell vamp with Morgana's passive. Now your Tears should be a little charged up start the construction of your Archangel's Staff. Last but not least the infamous, Rabadon's Deathcab.

Pros

Lots of Mana
Good Survivability
Lots of ap

Cons

Squishy
Slow early game

~How to play~
Now Morgana isn't terribly difficult to play, your damage relies on your ability to hit with her stun. Be mindful you don't have boots till a little later. Once you stun throw your soil at their feet and watch them as they are helpless for a few seconds. Black Shield will be your best friend, it blocks all disables. Stuns, Silence, Blinding, Slows, Trap. Won't affect you, and that's not all, it will take magic damage for you.Her combo including all should go like this, get close to your enemy, pop your ult, pop on your shield, follow them around till they get stunned, throw down your nasty pool of splooge and snare them in it.
~Teamwork~
You are a support character, stay in the back of team fights shielding the mates that need it. Snaring the enemies so they can't escape. Popping your ult when lots of enemies are around will get you targeted, quick so be careful when you do that.

This is my first guide. I played Morgana since level once and developed this build through those 30 levels. Feed back is appreciated.