Yes. Art of War, Res Publica, and Wealth of Nations should all come ahead of El Dorado. But I think he said he was already planning to buy those.@OP - Judging by actual content: Common Sense (Releases next week) > Art of War >> Res Publica = Wealth of Nations > El Dorado >>> Conquest of Paradise >>> American Dream, imo. Stuff like unit sprites aren't necessary since they do not alter gameplay.
I'd leave American Dream off the list, completely, tbh, unless you plan to play a lot of late game USA scenarios. If you're interested in the country-specific flavor packs, things like Purple Phoenix and Star & Crescent are more useful (if they're still available). Unit packs are something you buy on sale, if you have extra money, unless you're an immersion junkie.