Find the repeated task
An application is most useful when it helps someone perform a task repeatedly. Describe the trigger, the action and the result. Then ask whether a simpler web flow could do the same job before committing to separate mobile applications.
Design the difficult states
The happy path is only part of the product. Specify what happens when a connection fails, a record changes elsewhere or someone leaves halfway through. Empty states and understandable errors deserve the same attention as a polished dashboard.
Keep the first release small
Choose one complete journey that can be tested with representative users. Record what is deliberately outside the first release and what evidence would justify adding it. Assign responsibility for maintenance, permissions and data export early.