There is no right answer to this question. I gave you my assessment in my first reply. It just depends on your willingness to reroll a lot (100+ times), how quickly you want you want to be able to reach full strength (2 core SSR kamihime is better than 1), whether you want to be stuck with Fire by default, and whether you're willing to wait a month for the other +100% eidolons to release. Gaia is fine as a starter pick and most players would be satisfied with it. As long as you Miracle it at least 2x you'll have a strong team in 5 months.
There's also the matter of we don't know which kamihime will be available with the upcoming Miracle tickets yet. Just have to wait and see.