Mobalytics - Support McGinnis by Naked

Can buy Healing Rite into Healing Nova first if you are out poked in lane.

Compress Cooldown allows you to use your heal more
Rescue beam can save your team in sticky situations
Healing Tempo will allow your team to put out even more damage
Heroic Aura provides a bullet resist aura as well as give your teammates firerate.

Plated Armor and Inhbitor for your last two flex slots
If you dont have the flex slots you can sell Healing Nova and/or Cultist Sacrifice for Scourge and/or Divine Barrier
Otherwise you can upgrade Expansion and Duration.

Debuff Remover against heavy CC/Debuffs
Counterspell to deal with many different spells
Vortex Web or Decay to provide some utility to your team can sell Healing Nova or Cultist Sacrifice for them.