I was in fact worried on not getting all the gem locations because no one seemed to tell me the right location of the courage gem when I was looking for it, but I ended up finding it.
My last Courage gem was found in the cave linking to the small island on mercay Island, how theres that long bridge. In the middle of the birdge you use the boomerang to find a switch and you hit to make the cheat containing the courage gem appear.
Anyway.. If I had to choose upon one spirit, but not all of them, that would be the Courage spirit because Ceila is also the spirit of Time.