Thanks for the compliments. I realise a game like this profits from much more tutorial, this is what we could manage in the time ;)
You got the basics right: You send out the first follower to recruit more, then send the new guys to do tasks all around the cave that grant different bonuses, like altar offerings being eaten before cultists, monuments being shields when attacked by other Elder Beings, etc.
Yes, locked items likely meant you did not meet the requirements to tackle them. Many cannot be unlocked in the first few rounds because all you can recruit are illiterate cavemen.