This is Max from the Shopify Team.
The easiest way to approach this is by creating collections and linking them within drop down menus. Check out this help doc to Set up drop-down menus in your online store.
Collections are simply groups of products. You can name and arrange them accordingly. There are two types of collections that you can create:
You're then able to create a hierarchy based on the items within your collections. For example, from broadest to narrowest Shop All > Apparel > Women's > Women's tops. Each step is a different collection and some products would and should be repeated in multiple collections.
The Debut theme can easily have dropdowns added. The preview of this theme shows an example of the look of a dropdown under Catalog:
If you're looking for a more sophisticated step down or search than the regular dropdown menu format, I'd suggest looking into some apps like these to help with filtering and menus.
If you need any more clarification, please let us know!