Now that I finally have access to unlock functions in Phase 4, what should I unlock first?

Increased hospitals and army caches

Faster Digging if you want to get to digs fast, either 1st or 2nd
Better Hosps for more convenience and (much, at this point) faster idle completion time, recommended first
Inc Army Cache for again faster idle completion time (+battle +early game cache jumping) recommended 2nd

Thanks for your input!

I start by taking increased cache armies up to 50% or more.

Then I split my AP between that, and better hospitals, and cache visibility.

Once those three are maxed I might unlock simultaneous levels, or max out auto-draft.

What happens after that largely depends upon whether I intend to play WZIB.

Thanks for the help!