Category/Sub-Category data model

Question:
I am currently building a site where members can submit items and I want to create a two-level hierarchy so they can categorise the item.

Product:
Wix CMS/Database

What are you trying to achieve:
I want to create the right data model so it aligns with the Wix front-end. I want user to select a category and then a sub-category.

What have you already tried:
Not much yet but normally I would have a taxonomy but Wix does not have one!

Additional information:
None

This can be achieved using code. It is specific based on what your requirements are so not really cut and paste. I have built directory sites with similar requirements.
like the attached image. the member has to select a Category first and then the Type dropdown is enabled with only selections from that category. It then populates the list below with what has been selected.

This can then be used in a repeater to search and sort by category and type