You must follow the below steps in order to invest in pickup delivery app development: 

1. Planning and defining app requirements
2. Designing the user interface (UI) and user experience (UX)
3. Developing the backend server and APIs
4. Creating the front-end interface for users and drivers
5. Implementing location tracking and mapping functionality
6. Integrating payment gateways and third-party services
7. Testing and debugging the app
8. Launching the app on app stores