As soon as you have enough gold, spend it on upgrades or a new plot. You have to spend gold to earn more gold. To progress while away from the game, purchase automated upgrades. Each plot has one available, and are purchased separately. When actively playing, you have to manually collect money from a plot after it finishes production before it can begin producing again. The automated upgrades allow plots to continue making money after their production cycle ends. After saving enough gold, you will be able to purchase triple multipliers. They triple the earnings of a single type of plot.