You have several types of resources. Shells, laminaries and money. To keep the business running you need pay the the bills with shells.
The toll raises each month. So you need develop shells income.
You can build and upgrade constructions which produce one resource and consume another. To build and upgrade you need money So you need to develop bucks income.
You start with building and upgrading (click to the building, then click upgrade) farms in empty slots (squares with plus sign) to pay the rent. Then you need other resources to develop so you build other type of buildings.
The challenge is to find combination of buildings to handle resource streams in a balance at given time. Then change buildings when situation changes.