We have on-topic categories, and three categories, want to buy, want to sell and off-topic, which I’d like to exclude from suggestions. The on-topic discussions can in my opinion be cross-promoted, while the second hand categories, which are very busy, are explored anyways and usually push other topics off the list.
The off-topic I just want to hide, not because I want to discourage off-topic discussion in any way, but simply to keep attention in the original context.
It’s a good question though is the on-topic categorization too fine grained, and should, for example tags, be used instead, but I’d like to hear some thoughts and best practices on this before making any big changes or restructuring 
no it’s not 