Hello, I'm Main Got Nerfed and I used Morgana to climb to plat in flex so I'm going to teach you how you can use Morgana to climb too! (Season 8)
Op.gg: http://na.op.gg/summoner/userName=Main%20Got%20Nerfed

Pros

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VERY easy to farm with.
Great assisting with ganks!
Safe with black shield
Good pick potential

Cons

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Low Auto-Attack range
Can be difficult to land Q against ranged opponents.
No mobility spells. Kinda slow in general.

Arcane Comet gives you additional damage, and if you hit your Dark Binding, your opponent will be unable to dodge it. This keystone scales well with AP.
Summon Aery This keystone is not bad at all. Comet is hard to land in the early game when you're just poking with your W, but Aery will always hit! In addition, you can give your allies a rather large shield since the shielding part of Summon Aery scales well with AP. This is a very viable option.
Manaflow Band- Fairly standard choice for mages. Morgana can easily stack this due to instant cast Tormented Shadow with a large radius. I will try the other runes in this branch soon.
Transcendence- Fairly straightforward. More CDR = more power.
Gathering Storm- This rune really turns on after 30 minutes. If you think the game will go late, definitely take this rune. This runes also compliments a more passive/farming play style.


Perfect Timing If you play on building Zhonya's Hourglass at all, take this rune. It lowers the cost and lowers the CDR of Zhonya's. An all around good choice since Zhonya's works well with Morgana.
Cosmic Insight More CDR = more power. And this gives item CDR (compliments Zhonya's) and summoner spell CDR. What more could we ask for?

When should I build Zhonya's Hourglass?
Generally speaking, you should be building this item against assassins like Zed, Talon, etc. You can also build this item against one shot mages like Syndra but it's less effective of a purchase because it gives armour, not magic resistance. Even if the enemy doesn't have any of those threats, this item is still a good purchase because it lets you flash -> R Soul Shackles.

When should I build Void Staff?
According to the lolwiki, void staff is only gold efficient against an opponent who has 90 magic resistance or more. This means against tanks or sometimes fighters like Jax.

When should I build Morellonomicon?
When then fed enemy has healing abilities or has purchased life steal items. Like a Fiora with Ravenous Hydra or an enemy Draven with Bloodthirster. Always build this against Vladimir and Dr. Mundo.

Morgana gets much stronger once she has a couple items under her belt. Therefore, in the early game our main objective is just to push waves in, recall, repeat. This becomes increasingly easy since your level 3 W Tormented Shadow can kill caster minions with a single cast (with a little AP)

You should be shoving waves in with ease. The reason it's good to constantly push waves in, is so that the enemy mid laner never gets a chance to roam. If you farm under tower, the enemy mid will most likely roam bot and get fed. Shove shove shove!

You should be grouping with your team because Morgana is not a good split pusher. Landing a Dark Binding on any enemy will likely lead to a fight or in the very least, a kill.
Also, you can farm the raptor camp quite effectively with your Tormented Shadow assuming you have some AP items finished. A single W can take out the little chickens, so just finish off the big one with a Q. If you feel safe enough, steal the enemies raptor camp!!

I hope you learned a thing or two from this guide! If you have any questions or comments, leave them below and I'll try to get to them as soon as I can.

Thank you for reading.