One of the most important components of the KonMari method is to sort through your belongings and keep only what "sparks joy."
I've found this a surprisingly useful guideline to follow.
Even when it comes to mundane items that really don't have much to do with joy, I've been able to do thorough tidying because of the KonMari method. It definitely helps to sort by category. I think it's because when you go through all of one type of item, you realize just how much of it you don't use. So I sorted through my cleaning supplies, which were scattered all over, and realized I had three bags worth of hazardous materials to drop off. (Locals, here's a list of locations where you can take your hazardous materials in Los Angeles.)
The thing is, I'd actually done this sorting a few years ago and had acquired only a few new items between then and now. But the other items that had survived the initial purging and are now gone were items that "might be useful." The kind of thing I felt kind of bad about getting rid of, since we might need it at some point. That's pretty much the opposite of "sparking joy."
And what I realized after I'd sorted, discarded, and re-organized was that I felt genuine joy in those areas where my cleaning supplies are stored. All that's left is what I actually use. And because I store like items all together now, I can see how much of something I have. For a practical, frugal stockpiler like me, that's a deeply satisfying feeling.