Show categories both on homepage and on categories page?

I'm creating a "directory" website that has many pages, each belongs to a category and a sub-category.

I have category pages that will list all the pages that belong to the categories.

Example:

example.com/categories/blue-widgets/

Will show user all blue widgets (100 items - each links to specific page)

example.com/categories/blue-widgets/blue-mixed-with-red/

Will show user all blue mixed with red widgets (similarly, 20 items).

This is supposed to be good also for SEO, to make the first level accessible to the crawler too.

But under this logic, I also have to make example.com/categories/ accessible, and I don't want to show all 1000+ items in this page, because it's too much, and not useful for users.

So I thought maybe displaying in this page only the categories and sub categories, but this is exactly what I plan to do on the homepage, so I think it might be silly and wrong-SEO wise to have this kind of duplicate.

If I make a 302 redirect from categories to the homepage, that also doesn't feel right.

So, what is your suggestion, SEO/Content/UX wise? It's important to note my main concern about this page is more in the SEO perespective.