Focus on the stuff you can use right now, then move on to things you might have in the future. RNG is a fickle thing. You might have nothing for one element today, and then suddenly a couple of gacha pulls have the P2W Eidolon and 2 core Hime of that element. Does that happen often? Hell no, but it can happen.
Ultimately, you'll need all of them. If for nothing else, T4 Souls require a fuckboat of materials from all elements.