1. Don't worry if you can't clear all 5 stages of GO. The missions you can clear are simply challenging the order, and being able to clear stages 1-4, which will net you 1 orichalcum.
2. To clear GO reliably, a good gauge is when you're able to clear AQ4 without issue and without a 100% eidolon. Without issue is important here, as GO is pretty much harder than AQ4 at this point.
3. The trash mobs here are about as strong as AQ4 trash, but with a bit more lethality in their skills. Manage your skills properly so you don't go into the next stage with your skills out of cooldown, but make sure you don't get killed either.
4. Trash mob priority is
a. Stage 1
Upper, Lower, Middle
b. Stage 2
Middle, Upper, Lower
c. Stage 4
Middle, Upper, Lower
5. Boss strategy:
Debuffs work here. If you can one shot the boss, you don't need to read this. I assume you can't. Firstly, note that in week 2 you must clear this in 15 turns as a mission requirement.
The standard treatment of this boss is to land your debuff skills and soft hit the boss with normal attacks till she's almost at rage. DO NOT push her into rage with normal attacks yet. Poke her with a skill with enough damage to push her into raging, then unload all your nuke skills and your full burst. If using Hercules PF, make sure you use PF one or 2 turns before this phase.
Hopefully you should kill her, because her rage trigger is a HUGE AoE dmg that some of you guys have eaten already. If you follow everything, the boss should be dead, or almost dead and stunned, and you can clean up with your barely surviving team, or with your 2 backup girls.