morgana is super fun! and honestly i think shes a super well made character, who is sadly misunderstood by a lot of players. shes a great battlemage/control mage, but her potential is locked behind knowing how to hit and/or hold your q's and how her shield only blocks magic damage.
a lot of people build her like an enchanter but shes just not an enchanter. she has great ap ratios (her ult does +140%ap if you land the stun!) and what use is her passive 20% spellvamp if you dont do damage. She can absolutely get supportive items, like locket and ardent, but you dont rush those, theyre situational. But dont go grail. Your shield is your only way to proc it, and it's cooldown is too long and its just too valuable to go blow it to heal your adc whenever its off cooldown. another thing about her not being an enchanter, aery is eh, you dont have consistent enough poke in most matchups to make it worthwhile, and same issue with shield cooldown being long. guardian is only good if you have an ally with you, and the rest of resolve is very subpar.
Another great thing about morgana is that its super easy to invade the enemy jungle when your lane is pushed up and steal camps. a while ago they buffed her W's damage to monsters, and her spellvamp applies to large monsters, so its a very solid way to pick up extra gold and put the enemy jungler behind.

pros- free sustain in passive, block literally any and all cc for anyone on your team, 2-3 seconds root on a 5.5 second cooldown, her ult basically tells you if theres an invisible enemy nearby, big burst and sustained damage

cons- not as good against physical damage, her value is based on landing q's, runs out of mana if you are not careful earlygame, can be vulnerable to getting burst and chain cc'ed,