Where should I focus my attention for gear progression while playing solo?
Your best option is, of course, to ask for help. If your friends are well geared, they can likely get you decently set up in an evening or so.
If you do have some Hallmarks/etc to work with, then grabbing the NQ Ayanmo body and upgrading it to +1 would give you something solid to start with - not the greatest offensively (or the best use of fibers, which are ideally saved for +2'ing), but it remains good as a DT/Hybrid item, and it might be the most effective move for you right now.
I would also expand the goal to general progression. Apologies if this is stuff you've already done, as it's hard to tell:
Spells. If you're lacking key things like Mighty Guard (as that'd need Abyssea progression), then that's something to work on. There are actually a number of spells to go learn in Alluvion Yorcia Skirmish too, with the side benefit of possibly getting some gear to augment. So, I wouldn't write off doing that entirely.
Similarly, if you haven't built a nuking type setup for BLU, try to pull that together - a lot could be used for SCH or something too, if you want to try changing tactics for solo. If not...
Job points. BLU benefits
greatly from several of the job point categories and the 100/1200JP gifts. They're slow initially, but, if you're not at least at SU2 on BLU I would push on that before trying to solo much. Outside of Apex groups, AoE nuking is the way to go for this on BLU.
Voidwatch/Walk of Echoes: Or, more or less, have the ability to
unlock Empyrean WS. Similarly, there are Mythic WS to unlock (more important for your COR) if you haven't.
+2/reforge/etc your Relic feet. Ties back to Mighty Guard in particular, as the augment on these increases duration on Diffusion. Between these and the corresponding Job Point category, you can push Diffusion'ed Mighty Guard duration to a little past 5 minutes. So, means that Unbridled Learning will be back up when it wears, or you can alternate with Entrusted GEO Haste.
There's also the other still-useful older items like collecting gorgets/belts/etc for Fotia items. Or, if you haven't, getting out to various zones and HPs to ensure ready access if you do line up some help.
More or less, if you're playing more than the folks that can help you, then maybe work fleshing out other stuff while they're not online. Some of that contributes significantly to your overall capabilities.