At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga.
Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus.
Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
I'd probably go with the third option - conquer more land.
The reason why is that the Incan rulers were considered divine with their own religious cults formed around them. When they died, the eldest son would inherit the political power of the empire -- but the other male heirs of the family would inherit the lands that their father had conquered during his time as emperor. This would be referred to as "split inheritance" for the Incans.
It was similar to the Egyptians burying vast treasures that belonged to the pharoah in Egypt, only in the Incan's case, the land that they conquered in life was technically still theirs even after death and it was up to their descendants to care for them. In this case, the other sons who did not become emperors.
So, to build up their own land -- and to prepare a place for their own divinity and sons -- new rulers often had to go off and conquer new lands that would pass down to their family when they died.