Not sure where you have the 1 fairy thing from. For instance I have 15 of them at present (I admittedly used a few when I urgently needed to level a black unit for an event, but other than that I've hoarded them), which is enough to level a sapphire from low 40s to 65 after CC, compared to needing almost twice that if I was using other fairy types. As for storage, I just leave them in the gift box. Things in there last indefinitely so long as it doesn't fill up, so why retrieve gifts I don't need yet? There isn't really a good reason not to save them unless you desperately need spirits to level something in time to complete an event.