Yeah, you didn't get Gaia from gacha, you scrub. That makes an entire world of difference.You'll need them for FLBs, which once piled up make a world of difference in power. Not sure how many FLB-able weapons you have, though.
And it's hard to give advice on whether or not you should run Fire or Light against this, since we know next to nothing about your account. What kind of Grids do you have for these elements? We know you have Maid Amon and Prometheus, but what else?
And I guess most importantly... have you tried running GO with your Light team, and kind of a problem do you run into?