Databases can still be valuable with incomplete records. A catalogue that contains a skeleton record for each item is still useful as it captures that the item exists, even if the full details have not yet been captured.
Allowing contributors to build on and improve existing contributions makes it easier to share the work of collecting and maintaining data. It also lowers the barrier for new users as they can focus on improving existing records, e.g. via Suggested Edits, rather than adding new records.
Encouraging users to add basic records, then later improving the depth of information available, will help to ensure the dataset can quickly grow and demonstrate some value to contributors.
A record is likely to have some minimum data requirements, so be sure to clearly label required and optional fields.