Gear really isn't as crucial for Amdapor Keep as a healer. They're mainly DPS checks, although you chipping in with Cleric Stance and some nukes can be incredibly helpful. Not that I'd expect a first-time healer to be doing such bold things, but it's an option if DPS proves to be lacking.

Though in general, some pointers I suppose...

Your relic should be a long-term goal. No-brainer, I guess. Start the questline if you haven't and check the Market board regularly for cheap Quicktongue III materia if you don't plan to Spiritbind gear yourself. While you're working towards the relic weapon, a cheap Madman's Whispering Rod will do fine and fulfill half the requirements for your relic prerequisite weapon. Once Amdapor Keep is done, you can buy a Grand Company Weapon that's nearly just as good as Ifrit's Cane, though you'll need a shield to go with it. Other than that, you can continue farming Ifrit/Garuda in hopes of a drop.

If you did some levelling through dungeons and finished the main scenario, use your Allagan Tomestones of Philosophy to get yourself either the Darklight Sash of Healing or any of the accessory/jewelry slots. If not, you can begin doing some Castrum Meridianum or Praetorium runs for a few quick Tomestones. Failing that, check the Market Board for Turquoise (Mind/Spell Speed) or Tourmaline (Mind/Piety) jewelry. I wouldn't be surprised if your accessories suck, and seeing as you already have a full set of Artifact gear, armour isn't that much of a priority.

Once Amdapor Keep is done, I suppose it's time to just start the long path towards a mix of Strategos and Darklight gear.