I only play huge maps, so there might be a few more ruins than normally. Under such conditions I find map reveal followed by unit upgrade the strongest. The first one gives your pathfinder 3-4 levels immediately from revealing tiles. It allows to take trailblazer I+II followed by sight I+II really early, giving huge speed advantage and increasing exp gain/probability of finding more ruins exponentially. I follow that with +1 movement and then Survivalist I+II+III as fast as possible. If you upgrade to Scout, you get +1 more sight, again speeding things up. Then with auto-heal every turn (survivalist 3) it can clean camps on its own and tank cities without walls (useful with archer rushes). The second tier of huts are production(especially for getting this first monument out faster)/faith/tech. Tier 3 gold/culture (very little culture usually) and pop/land which are pretty situational. Bottom tier - unit experience.