The best thing to do is constantly upgrade and purge. Smaller scales really help, although I miss the detail in a 28mm figure. Stick to one scale as well. I got rid of all my 28mm Star Wars after I decided to go with 15mm. It was really hard.
My father was an incredible hoarder, to the point I’m not sure he really knew what he had. When he passed away suddenly I had to get rid of everything. The one thing I noticed was that he had so many multiples of the same thing. If you don’t use it, get rid of it..
I found these cool storage bins with a shallow tray that sits in the top. I can put the bigger pieces on the bottom, and some of the smaller stuff in the top.