Many players advise to max out your offense at each age (just the troops/tactics you actually use) while paying little attention to resource and defensive buildings. This works well if you are an active attacker. You can build resources through attacks much faster than farming. And as pointed out, you can never build a base that can stop Age+ attackers. Your best defense is to build up and spend quickly or to be under a peace treaty. I recommend to build your base with the City center on the edge and hope for defeats to limit resource raiding. There’s nothing worse than getting your resources stolen over and over without actually losing any battles to gain treaty protection.
My looting strategy is to drop medals by raiding without getting any stars all the way down to 200 medals, then building a full army and rolling over weak bases with minimal losses on the way back up to around 2000 medals. I can usually fill up my resources in a few hours with training blessings running. Then it’s just a matter of prioritization and build times.
Personally, I like the defensive aspect of the game so I invest a lot there. Unfortunately defense is irrelevant in the current RPG/AR meta, but perhaps this will change.