I also didn't know what to do to get the gym my first couple of playthroughs. Even with the tutorial I struggled, and I only figured it out on my 3rd playthrough. I'm sure they'll add more days as they keep adding content, so I'm not really too worried about it? I still have not been able to finish Asterion's project no matter what I try though! It makes mesad lol poor moo.
But that's a good idea to possibly add a time to assign roles while in the Hinterlands.