Do you have anything you can show at the moment? Even a roadmap?, a kanban board? a GitHub page?
Any details on what the project actually is and the vision of what that is going to look like? What problems this is solving?
Is this a mobile only project? Or will there be a webpage? Do you already have designs in place or will contributors be able to exercise some creative control over the look and feel?
Is there a backend? Is it already complete? Is it just using rest APIs or some other pattern? Do you have documentation on how to connect to a QA or Test environment or how we can setup a test environment for ourselves?
Is this going to be a FOSS project or closed source?