Drake Hollow

Improvements are anything that you can build within your village. Everything from bouncy balls to greenhouses will count. That being said, it is very likely you will acquire this through natural progression of the story mode. However, if you're looking for a super quick method, then I would advise building the cheapest improvements repeatedly. Grass beds and bouncy balls are pretty cheap, though it will require you to go out and collect enough resources and you don't always get 100% of your resources back, so heed that advice.