doombotmecha

I'm guessing you might've already figured it out, but in case you haven't...

I'll let you know that this game is designed for you to have a full team of battle-ready pokemon pretty much at all times, at least for when you're progressing in any way where pokemon battles can happen.  The fact that HMs can be forgotten for other moves without needing a move deleter means that having a Bibarel is amazing as Bibarel can learn any and all HMs except Fly, which is okay because the game gives you multiple ways to get around without needing Fly. (You probably only have access to the guy with the truck/car right now though.) So if you need HMs for progression then Bibarel allows you to maintain good movesets for the rest of your pokemon.  Bibarel also learns headbutt so it can do that to trees and such though I haven't found a notable use that I can remember at the moment.

The Exp. All should be your top priority item to get from redeeming Achievement Points, at least in my opinion.  Naturally, it allows you to EXP train/grind multiple pokemon at once, but it also lets you EV train/grind multiple pokemon at once.  Speaking of EXP, once you get access to the first Audino trainer/breeder, you'll find level grinding to be much easier, especially with the Exp. All and a reliable way to 1-hit KO those Audinos. (I used a Sawk.) I believe that the first Audino trainer/breeder is in Goldenleaf Town.

I personally got the EV Room Cards next, because to hell with it if it's possible to get them later in the game once you have multiple HMs and access to the areas where they are.  I'd like to have the pokemon I plan on using to have their EVs done and ready to go, so that down the line, when average levels are in the 40s and up, I don't have to go and catch replacements, because the pokemon I were using needed EVs from rooms I didn't have access to at the time, so they ended up with random ass EV spreads that will hamper their endgame potential. it just made sense to get access to the rooms ASAP so I could really start banging out the EV spreads I wanted and not have to keep so many potentially useful Pokemon in the PC.  So I'd say go EV Room Cards next after the Exp. All, but you're free to do as you please.

I actually did get the exp all in order to grind to 25 for Keta I. I skipped the audino in favor of the fletchinder and Kricketune in Sheridan Arena, so I could get more attack and speed EVs.

I may get the special stat EV card next, but I'm also thinking about saving up for the Golden Axe. Nothing on my team rn learns cut, so I've been lugging around this Dugtrio through most of chapter 3. I should definitely EV train it, but rn Marshtomp is kinda all the ground I need. I had been excited to add Zangoose to my team, but it doesn't learn cut for some ungodly reason. I might actually pick up a bibarel for this game. I guess Reborn is just really light on hm use compared to rejuv; now that I think about it, most of reborn city only uses hms for bonus areas, like the rock Smash bits under the grand staircase.

To answer your earlier point, I think "battle ready" means something different in c2 rejuv than c2 reborn. As I said in my other post, I would have been pretty comfortable taking my initial Keta I team right into Florina. I think another part of it is that the game takes into account that you may just buy the exp all right as c2 starts, meaning all the double battles are made with Max level mons in mind.

You should be able to get a Bidoof from Gearen City and evolve it into Bibarel for HMs. (Really like did you not come across one?  I came across like 50.)

Personally I don't think the Golden items are that useful as early in the game as you are.  The story does sometimes require you to have an HMs handy for progression, but from what I recall, the game allows you to have 6 good mons for most tough fights, and the ones where I needed an HM to get to the fight they weren't hard enough that I suffered too much for it.