Well, we've been slowly introducing concepts since he was 5. I started showing him how deckbuilders work then, and he's getting pretty good at Legendary. So now we're working on resource management, which also ties in to teaching him about money and finances (which I waited to introduce until he was pretty well along in math). Long-term strategy is the next idea we'll talk about. The most important part for us is him having fun - I'll also have to remind him that I've been playing a lot longer than him, so naturally I have an advantage.
Thanks for sharing! This is one game I'm looking forward to playing with my son as well. He just turned 5.. I'm curious, at what age did your son start grasping the more complex/advanced nuances of board gaming?