but that's the thing... what's here now is either a lucky gacha roll or rerolling to get marm... otherwise hopefully getting thunderbird or take/behemoth (but you'll need more of them)... the current light eidolons you can get now without backtracking sucks...
they can take what would benefit them more.... this involves paid gacha in some way, or dealing with an SR eidolon...
main focus should be stats honestly when starting out cause again, you can wait for the right stuff to go after, but will you have the power to go after it since you avoided previous things? cause as a new player, you probably can't even farm expert disasters for a while to even get a grid full of assault.
and again, rerolling is a thing, but if they're aiming to go for light as the reroll, then it'll be a while cause it cuts down the target eidolons from 5 to 1, and at those odds... you'd best be patient. plus you're more likely to get something better for a different grid, and if it's not dark (likely since we don't have that 100% eidolon yet meaning echidna/ouroboros is the best you get right now) then you got a weakness to deal with meaning a definite 2nd team to build up to start getting your footing in the game...
you can have an endgame focus all you want, but if you're lacking the resources to go after it, better go get them first. ultimate advents is clearable off raw stats alone. and assuming you're playing entirely free, you've got months before getting a kaiser and that's if you grinded out all the SSR Eidolon copies you can get. Weapons you can be picky on (we get 2 SSR per advent), but you're just making it that much longer by not getting the eidolon either way