It seems that the weirdest and most narrow fields of interest can yield the best and most interesting collections. My wife started years ago, collecting “snowmen” any time I found a vintage looking or ugly looking or weird little snowman, I’d grab it for her. I was her snowman picker. Now every Christmas, she has an amazing snowman tree full of unique and some very old and classic pieces. It has grown beyond the tree to an entire bookcase
and the tree full of snow people. It is a pleasure to look at. We have grand kids that marvel at the scenes.
I collect old radios, and some old radio “niches” ie I collect tubes, and I collect early radio advertising and radio parts advertising items. Do you see how you can become more and more specialized into tiny little branches within your main field? The finer the niche, the more unique and interesting and valuable your collection can be!