True God
On jewelry, all resources looted, followed by oil looted and then national trade good chance. And given there aren't that many jewelry options, it should be reasonable to find artifacts that have one of those at 11% in the first slot and other good ones at 6% or higher before upgrading anything.
On armor and weapons, my focus is on defender spawn times and stats (improve mine or worsen theirs), and fighter HP/damage, since those are so vital. Ranged siege or infantry damage can be worthwhile, or tank HP if you run them as decoy bait. But in general, boosts that only apply to a small percentage of your army aren't going to be very valuable. Harder to decide on upgrades here, as the number of possible combinations mean you may never find anything great.
The pots seem to be good for oil from oil wells, and vault interest. But nothing else is really useful. Vault capacity is stupid, as it adds that percent to the base storage capacity of 2400 oil instead of to the total 12080. So worth a few hundred extra oil stored at most. The interest is on the entire 12080, so 11% is over 1000 oil. I wouldn't spend resources unlocking additional levels of these; I might spend blueprints upgrading one with 11% of one of those two stats in the first row. But not a lot of them.