[Gregstrom]

I'd think a better point of reference for costs would be one of the elemental royalty.

At 50 gems, they have 4 or 5 levels of magic and are SCable with a further 20+ gems of equipment. They don't have full slots, and you can only summon limited numbers of them - both factors which I think would reduce the gem cost of the summon a little.

Since you can get unlimited numbers of spirits, you don't need to equip them to use them as SCs and they have a lot of magic, I guess the cost should be over 50 gems.

I guess they probably aren't seraph-level, so a cost under 100 would be sensible. 60-70 gems, perhaps?