I love Janna, Nami and Soraka.
is great at keeping enemies at a distance while having some great backup plans and utility. Honestly, you could even give up boots for AP or an aura to make yourself more impacted.
is more of a duelist, constantly using spells to fight alongside your teammates while providing good cc and heals. Has her own source of damage too, and her ult is so good altogether in this meta right now.
is best for healing, as she can literally keep and ADC alive for double the time they should be. A global heal that could potentially turn around ganks in mid or top is awesome. She has the most to offer, and has even been dubbed "League's Healer" since get rework. She isn't great at the other stuff however, but she does great once you get to know her.
When it comes to playing support, these three are my go to. Keep these three on mind if you want to play a healer/shielder.