Making a profit in RollerCoaster Tycoon Touch involves putting in some work as your earnings don't automatically appear in your bank account. They literally have to be manually collected by going to your various buildings and rides and tapping on the coin icons that are above them.
It is important that you regularly check the status of your rides and buildings because each structure has a maximum number of coins it can hold and they will not be able to earn additional coins once it has been reached. Once a structure has reached its maximum capacity the coin icon above it will turn into a safe, whenever you see the safe icons you should make collecting from those structures a priority.
One way which you can get additional profit is by adding decorations around your rides. To get the most benefit from your decorations you should consider rearranging your park structures when you reach level 10. As for the profits themselves, you should only spend them on upgrading cards you use and things that will impact your profitability. It is also important to remember that in the early stages of the game coins are hard to come by so make sure you manage your finances wisely.