Categories, Subcategories, and Category page layout

Hi Gents

I'm doing an educational website. I've managed to wrestle the content down to a minimum of 'essential' categories. However, the content REALLY needs subcategories and a clear way to navigate them. Ideally in a responsive menu that works well with mobile (slideout?). Here's a quick summary of the bare minimum of what I'm looking to do:

1. Have the main categories as links in a menu leading to the 'archive' page for that category. (done!)
2. Have a visual, nice, soft landing in the archive page with a short tutorial or explanation (what I have now is pretty rough and the editor doesn't allow much customization)
3. In the archive page, have three subcategories for each category: beginner, intermediate, and advanced. These would lead to pages that filter the chosen category posts according to their chosen level (subcategory).
4. I'd also like this filtering to be possible with tags. For example, if someone clicks the 'brick' tag, they would see the three (beginner, intermediate, advanced) category links on the tag archive page that filter these out according to the 'level category'

Is there a plugin that does this? Or is there some straightforward CSS framework that could set this up?

Feel free to tell me if I'm getting too far into 'you better hire a developer' territory on this one. I would do this straight away but I'm bootstrapped to the teeth right now. :-)

Thanks

Michael