Mini Era Advice...

The big reason for investing in the Eras (from a GAC point of view) is the boost you get with new shiny thing and the datacrons that go with it.

This era there's no Legendary to aim for and the 2 marquees will go on a team.

As you have zero chance (I believe) of unlocking GL Mando early let alone day one, what would you gain from investing crystals into this Era?

Yes, you'd get more from coliseum, but would that work out as a worthwhile investment of your crystals compared to what you could do with them?  My feeling is definitely "no it wouldn't".

I'm 14 million in Kyber.  I have everything (the 2 newer Era Legos not at 7 star yet) and unless I'm missing something, this is a skip Era for me.  I can't unlock GL Mando on day one now, and these mini Era units are going to be farmable much more quickly than usual.

My personal opinion is that you probably shouldn't be spending your crystals on Eras.  However, my boat is a different boat so...I can't tell you what to do with your purple stuff.

Adelphi Ranger seems really hot right now, basically no non-GL counters to that team so that's a reason if you want to invest, I also think you don't need Adelphi Ranger at super high relics at Carbonite anyway

but of course everything I just said is theoretical, and there's no material benefits to investing in this Era, other than the units might be good in the Raid

Personal opinion, you should be investing in the new Raid.  I would be, and am, doing everything I could to get the first set of era toons to R6 to unlock Maul - Cash Fueled.  I’d also, and I am, start investing in New Republic to R6 to get Rotta 7 star when he comes back.  I just need Grogu and Snowcone Commander to 7 star.   Both are at R5 for me.   Rebel Fighters and ISB would be last to get to R6 but that’s just my opinion.  

I'm just shy of 15mil and I will get GL Mando as soon as I can, I've been getting 5* for the era toons, but I'm only going to 4* the mini era because the 5k crystals will be better spent on shipments

Throwing in my tuppence worth, as I think my level might be similar to yours God. I’m currently bouncing between C1 and B4/5, and I get 400c daily from fleets. I rejoined the game with a new account after a few years break at the start of the New Republic era.
I invested in getting the era units this time around to 4* and unlocked DJJ, but mostly for the LSTs from his event. I don’t know how competitive my era shard is, but even with DJJ I only had about two weeks of breaking the top 90 and otherwise I’ve been top 250 daily, much like the era before when I didn’t bother with Rotta (mostly through ignorance, but also as I needed crystals chasing executor).
I’m not going to invest in the mini era because GL Mando is a long way away, and I don’t have the omicron mats etc to make the New Republic team make that much of a difference in the short term in GAC and TW, and without relics I can’t use them in TB. Instead I’m using my crystals for lots of refreshes on energy to get new republic and a few other teams ready for raid, alongside lots of my regular farming. That way I hope to have teams ready to hit at least 1m in the new raid, and I can continue to pursue GL Leia and Starkiller who will probably make more of a difference for me in GAC, TW, and TB. I’ll go back for the following era to try and 4* the legendary again.

Okay, I probably will not be going for them, then.  harvestmouse1, GreenSunRedMoon, CommanderBarcara, ScoundrelRui01, and Notthatotherguy... thank y'all for responding!  CommanderBarcara, I was/ an working on getting ready for the new Raid anyway, so I think I will focus more on that... and, as my Darth Vader (Duel's End) has been sitting at Relic 6 since about when he came out, I might as well get him some friends.  Notthatotherguy, Starkiller is very much worth it.  He was one of my first Journey Guide characters... and there was a pretty significant jump in my GAC score because of it.  As I mentioned above, Era of Anniversary is probably my biggest focus... however, I think ISB would be a really good team to have at a Relic Tier for Carbonite.  Since it isn't seen as much, hopefully it will make people waste a team.  Again, thank you all for reaching out!

Personally, I’m not going for AR because my Carson squad sucks, but I am going for new Embo so it’d be worth going for B1 merc for me.

I haven't looked at Embo's kit or B1's kit... do they work well together?  I should probably have known this by now... 😬.

There’s a lot of synergy, but unless you’re red crating hard conquest, and buying extra shards (is this also possible for cash?) then new Embo will still be 6+ months away in all likelihood for you. 

Okay.  I unlocked the Proving Grounds part way into the Conquest... so Hard wasn't unlocked for me.  I will try it out, however.  Also, no matter how hard I try, I cannot get the red crate... even on easy mode.  I can get the second to last crate on Normal Mode, however.