Using cards as navigation to other cards
I am trying to become good at web design, but feel I am missing that 'visual eye' that so many of you have.
The general flow of what I'm trying to make is a top-level subject (ex. Math), will bring you to a page of its categories (ex, Linear Algebra, Calculus, Discrete Math... and so on). You can then click on one of those categories to bring you to the actual content/tutorial/blog page itself (which will have a left side nav for different parts of the category). Some example on the side-left nav might if you click on Calculus might be .. integrals, etc etc).
I want to make a page where I will have multiple top-level subjects, all in their own card with an icon (and maybe a description). I've been stuck on this for a long time.
What comes next when you click on a major subject (ex. Math)? Another page with 5-15 minor-subject (Calculus, Linear algebra, etc..). Can they go in cards? Surely they must look a little bit different. I feel like clicking on a page with 4 cards, and going to a page with 10-15 cards would look repetitive and bad.
I only have 4 "Main subjects" so there is a lot of white space below. Maybe I need a light gray/blue background image on part of the page?
I am thinking about making those 4 cards a little bit bigger... and the next page they lead to have 10-15 cards about the original size of the 4 cards. Any feedback would be greatly appreciated!