So what worked for me was to focus on leveling up the throne as that increased the resources gain and then getting a barracks upgrade when I could afford it. The mine and farm don't provide enough value compared to those 2 and can be put off until the Throne and Barracks are maxed. Also each location has a different focus explore is random, the swamp is food, the mountain is gold, and the forest is a little of both food and money.