I think it's important to remember that even if you don't get the "best" relics, you can still do well in this game. There's a bit of an all-or-nothing attitude that surrounds this game sometime, and that's not the most productive way to think.
This is something that I've slowly been learning as I play the game longer. Back during the FF7 AC event, there was this sense of dread looming about future Ultimates, how tough SIN would be and what the best relics for the anniversary would be. With that in mind, I planned out and budgeted my mythril, but still took chances with pulls in banners that weren't "optimal".
What I was hoping to get ever since the FF7 AC Banners:
Any Hastega relic.
1st Fusion Sword
Excalibur (V)
Valiant Knife
Riot Blade
Sentinel's Grimoire
Genji Blade
Any of the FFT SSBs
What notable relics I got, along with comments about it.
Master Fist (VII) - which is the sole reason I managed to clear Bahamut SIN. Potent fist weapon even when lacking synergy. Dolphin Blow is incredibly strong, often leading to 9999x4 hits when under the ATK+50% boost.
Masamune (II) - Guaranteed blind has been incredibly useful, it's my strongest off-synergy sword at 123 ATK.
Moore Branch (V) dupe - While I was salty about it initially, I kept it in combined and it's worked great any time I need to double mage it up. Once I do combine it, it's gonna be my strongest caster stick.
Orchalcum (IX) - SSB doesn't play nice with Shout, but it's still a really strong dagger on its own.
Organics (VII) - It's no Fenrir Overdrive, but having a toy for Cloud Keeper is never a bad thing.
Wizard Staff (VII) - While the SSB itself is a bit of a stinker, FF7 caster gear is incredibly rare and it's now my most potent MIND stick when lacking synergy.
Peacemaker (XIII) - Your typical damage SSB, but on a solid gun which lots of new characters can get use out of.
Wutai Headband (VII) X2 - This made me cringe initially, but I haven't even needed to use the SB itself yet to make use of it. Combined, it's my single strongest piece of mage armor, Exdeath hat buff when.
Grand Armor and Kaiser Shield (FFT) - Do I even need to
Other relics pulled include Rune Mog, both of Zell's fists, Ebon Armor, Basilisk Claw, a Skycutter dupe and TONS of useful fully combined 4* relics, the unsung heroes of the game.
So while I didn't get a single thing I was hoping I would get, I still made out with a great haul that's gonna let me play around with tons of options that were previously unavailable to me. The lack of a hastega still stings, but that's been lessened by Wall not being as necessary for Ultimates as it used to be. I've managed to clear everything since Adel with just normal mitigation and good Hastega RW use. Obligatory / essential relics be damned. If I only listend to reddit's most optimal suggestions, I wouldn't have gotten as much mileage out of Exploding Fist R2 as I have.