Assuming that said newish player can clear ultimate levels in advent, since the other 2 kinds can be carried hard by union/ other ppl anyway...
Priority goes to half elixirs (to sustain more farming), good SSR weapons and eidolons, then to the jewels.
For events with average weapons and eidos, you could consider sitting the weapons out in favour for just getting the jewels. For the horus event however, this isn't recommended, cause fire events are few and far between, and you're not getting much of a chance to get any more fire weapons should you consider picking up fire in the future.
For events with trash eidolons and weapons, if you're a newbie you can just forget both, or one or the other, depending on which types are trash and not.
Finally, if you're not able to consistently clear ultimate, consider sitting the second (constant cost) weapon out, especially if it sucks or is meh. The eidolon and first constant cost weapon should be cheap enough for you to get, then it's jewel hoarding time.
Keep asking around which weapons are good if you can't decide.
Edit: Incremental edited to constant, I'm a dumb fuck.