Hello there. I'm a plat support main. I have been playing League of Legends since the start of season 5.
Morgana is my go-to support when our team is lacking AP and the other team has a engage support such as Nautilus or Leona.

Morgana is a very simple champion to play, so when you are auto filled into support I highly recommend her. She can carry games with her high damage output and she is good at dealing with the current meta supports (Nautilus, Blitzcrank and Leona).

Early game you want to poke with Dark Binding (Q) or Tormented Shadow (W) to get Manaflowband stacked. Just using your W on the enemy ADC is good as it will give you gold from spell thief's edge and scorch will deal extra damage to the target.

If against a CC heavy support, you will want to keep some distance from your ADC, this is so that the other team don't immediately change their focus to who doesn't have the Black Shield (E).

Mid game you will want to stick with you ADC, weather it being grouping mid, or swapping lanes with top.

Roaming mid with your jungler can work really well as you have a decent amount of CC and so your team could follow up for an almost guaranteed kill if you land your CC.

Teamfight you will want to put your Black Shield on whoever the enemy team want to focus (probably your ADC) or a hard carry that is susceptible to CC such as a Darius.

Landing you Q on enemy champions that are out of position can often lead to a kill as long as your team can back you up. Using W on the champion that is being CCed can do lots of damage and they won't be able to get out of it.

Using Soul Shackles (R) in the middle of their team followed by Zhonya's active ability will either force the enemy team to run out of the ability or stun them. They can't stop this as you are invulnerable and untargetable. Make sure to Q and W before you do this for more damage.

Landing a Q before using Soul Shackles almost guarantees landing your R on them as
cannot move for 3 seconds and it takes 3 seconds before it stuns them.

Your ult gives true sight and so reveal invisible champions, you can tell as you can't use R when no one is in range.

Sorry that this guide might be underwhelming, I am still learning how to make mobafire builds and I appreciate looking at this. Thank you.