Aery on Morgana is a reliable pick both offensively and defensively.
Offensively: You can easily and repeatedly proc Aery for poke damage with [W].
Defensively: Applying [E] to a teammate will also add health shield to your teammate on top of your Magic Damage shield.
Manaflow Band is a great rune choice is this slot for Mage supports because to provides a significant amount of mana sustain for lane harass and skirmishes. If the enemy team has multiple AP threats you can take Nullifying Orb.
Supports build a lot of CDR items thanks to the raw utility of their kits. More CDR = more power and with Transcendence you have no fear of over-capping. Celerity is a great secondary option for roams and picks.
If you choose to put a point in [W] early Scorch becomes incredibly easy to proc on cooldown for lane harass.
A free early Statis is a god-send for Morgana to land a huge [R]. The free Stopwatch also means that Zhonya's is that much closer to completion.
Doubling down on CDR and a little extra summoner cooldown for Flash->[R] is great here for Morg. Magical Footwear is also a great option here if you're looking to save money and hit combat stat power-spikes sooner.