Invest in increasing the energy level first, which lengthens money production times but also improves the maximum amount that can be stored when you are not in-game. If your Construction upgrades are too high of a level compared to the Power level, revenue will no longer accrue and you will have to collect it manually each time when the money is produced. When upgrading the Power Levels, note the small number in the upper corner of the building that is being upgraded. If those numbers are similar or higher than the number shown in the same location when upgrading the Construction levels, then you are safe. Get your Power to a new level first, then add ten upgrades. Follow this by upgrading the Construction levels all the way to the very end, but before switching to a new level. Next, catch up with the Power level and increase it and upgrade ten times afterwards, before repeating the entire process.