Keyflower. The core game play mechanic is very simple in that essentially everything is just bidding meeples that it is very easy to teach, but there is so much to consider, a ton of interaction, meaningful cost/benefit decisions, and so many ways to build up without being too much of a point salad. The game itself is very attractive on the table without being garish, and it can be kind of ruthless. It also scales beautifully, I have played it with 2 players and I have played it with 6 and its great everywhere in between. The iconography is clear and simple, the expansions are both great (although I prefer the Merchants for low player count and the Farmers for high).