Pros
High CC with Dark Binding
Very much harassment
Many flee opportunities, if played correct
Many opportunitet for teamfights
Late game high AP damage
Cons
Low mobility
Weak to take damage
Stunt shots, require skill

Soul Siphon
Passive - Soul Siphon
Morgana permanently has 10 / 15 / 20% spell vamp.

Dark Binding
Q - Dark Binding
RANGE: 1175 SPEED: 1200 COST: 50 / 55 / 60 / 65 / 70 MANA COOLDOWN: 11
ACTIVE: Morgana releases a sphere of dark magic that travels in a line, dealing magic damage to the first enemy hit and temporarily Root icon rooting them.
MAGIC DAMAGE: 80 / 135 / 190 / 245 / 300 (+ 90% AP)
ROOT DURATION: 2 / 2.25 / 2.5 / 2.75 / 3

Tormented Soil
W - Tormented Soil
RANGE: 900 / 175 COST: 70 / 85 / 100 / 115 / 130 MANA COOLDOWN: 10
ACTIVE: Morgana infects the target area for 5 seconds, causing enemies who stand on the location to take magic damage every half second, increased by 0.5% for every 1% of the target's missing health
MINIMUM DAMAGE PER HALF SECOND: 8 / 16 / 24 / 32 / 40 (+ 11% AP)
MINIMUM TOTAL DAMAGE: 80 / 160 / 240 / 320 / 400 (+ 110% AP)

Black Shield
E - Black Shield
RANGE: 750 COST: 55 MANA COOLDOWN: 23 / 21 / 19 / 17 / 15
ACTIVE: Morgana shields the target friendly champion or herself for up to 5 seconds, absorbing magic damage and rendering her target immune to all crowd control while the shield holds.
SHIELD STRENGTH: 70 / 140 / 210 / 280 / 350 (+ 70% AP)

Soul Shackles
R - Soul Shackles
RANGE: 600 / 1050 COST: 100 MANA COOLDOWN: 120 / 110 / 100
ACTIVE: After a 0.5-second delay Morgana latches chains of energy onto nearby enemy champions, dealing initial magic damage. The tethers grant True Sight icon true sight of affected enemies and Slow icon slow them by 20%.
MAGIC DAMAGE: 150 / 225 / 300 (+ 70% AP)
Targets who did not leave the tether range after 3 seconds are Stun icon stunned for 1.5 seconds and dealt the same magic damage again.

The ruins I use are pretty standard AP stuff. The flat armor seals are important because you will be taking a lot of physical damage early from enemy auto attacks and probably minions. The flat magic penetration marks are strong early as well, and help your damage a lot in lane. Because you have Black Shield, you can trade fairly well with magic damage-dealing supports early, so you can use scaling magic resistance glyphs. Ability power quints are fairly self-explanatory. I would say that a lot of these can be substituted based on your playstyle and preference, though.

Masteries are largely a matter of preference, in my opinion. I usually opt to go 12/18/0. The 12 points in Ferocity gives me useful bonus damage, and importantly gives a 3% damage boost to your ADC whenever you land a bind (or even get a single tick with Tormented Soil). The 18 points in Cunning give you a lot of useful utility. Meditation in particular is a great tool in lane that enables you spam your Dark Binding. Thunderlord's Decree is quite strong on Morgana because it procs with three ticks of her Tormented Soil, which gives you a fair amount of extra harass. 0/18/12 is also a very good option, though, as you'll get a base increase of 50 hp and most importantly a 15% cooldown reduction on summoner spells, so you can utilize Exhaust more frequently and is less punishing to use.

I choose Thunderlord's Decree over Deathfire Touch because you won't build enough AP to make the damage from Deathfire worth it, especially early. I've also seen and tried 0/12/18 with Courage of the Colossus, but I've found that since most of your Dark Bindings are landed when you're at a distance, you'll rarely get a sizable shield. Additionally, it won't activate on the first phase of your Soul Shackles so it won't help you survive burst if you choose to engage with it.

Like ruins, though, these are very open to change, and I do tweak mine from game to game to best suit the situation.

While starting and maxing Dark Binding is almost always best, what you choose to level second changes game to game and requires your own judgement. Does the enemy team have a lot of crowd control? Do a large proportion of their champions deal magic damage? Max Black Shield second. Otherwise, you can focus on Tormented Soil to help poke and deal damage in lane.

If you don't plan to invade and want to play safe in lane, you can start with Tormented Soil to capitalize on the gold income from Spellthief's Edge at level 1. However, this means playing extremely cautiously until you hit level two where you will get at least some usefulness in lane. I personally do not subscribe to this playstyle.