So, I kind of did the same thing way back when. Mostly played support and mid.
Morgana is totally fine to use mid and is super forgiving. She farms really well. Pretty much can go RoA into zhonyas every game and do great. Late late game she doesn't do as much damage, but she controls objects really well and her Q hits like a truck. Plus you already play her!
I'd definitely look into Lux - she's quite like a support. Has hard match ups though.
Orianna is really good also. She's a bit hard to play at first because of the ball but not difficult when you get used to it.
You might like Anivia too. She's a solid control mage, her lane phase is a little hard pre-6 but she's very strong and does a lot of damage.
Karma is similar too; she's hard to carry a game on though as she doesn't do a lot of damage late but really turns into a strong support late game. I've had a lot of success int he current meta on her. (You may already play her too). What I like about Karma, who is quite similar to lux, is that she does a better job helping ADCs I think than Lux does who sets picks up better. Plus Karma has some mobility in her kit with her speed up and is great at kiting.
Annie is also a really simple mid laner to play and worthwhile to pick up. She has some hard match ups but there's ways to play around it. And she can teach you a lot about roaming and going in and such.
Ziggs is also good. Poke heavy but a lot of fun and strong.
