You can upgrade the Coin Upgrades, Power-ups and Pets and Places categories. Start with Coin Upgrades first to increase the amount of money you can earn. Start from top to the bottom, focusing on the multipliers because they will result in more coins per tap. Also upgrade The Mighty Toss must a few times for the same reason. Next, purchase the most profitable Passive Coin Upgrade. They will allow you to earn money while you are not tapping. Next, consider some Power-ups. The Rush Hour Upgrade is probably the best, as it can be increased to give you more money and last longer. Rush Hours are very profitable.