Reading through the forums and updates it seems like Joint Strike is generally considered a strong upgrade and that makes sense because it applies to all armies and most situations, plus it scales well overall

after that what would be the next 3 most valuable buys? set aside offline time since that's up to preference and also set aside the gain more AP since it doesn't seem to have worthwhile RoI. what's next? army camps? mercs?

I maxed joint strike first and then went for mercenaries.

Agree on mercenaries after JS.

I also think it's worth unlocking the army camps, increased money from caches and decrease mine upgrade cost are worth unlocking. I wouldn't max any of them until you've gotten much farther but they value/AP is pretty decent.

Edited 11/7/2020 21:22:53

This might be an open door, but extra idle time is really nice. I suggest you upgrade it to at least 4 hours.

Oh yeah, higher money cache rewards are cheap to upgrade at first too