I try NOT to collect things, keep using the "Life-changing magic of tidying up" book's advice to keep shoveling things out the door I'm not using.
Besides, I live in a one-room apartment now.
1. photos of birds and wildlife I've taken, but store them in the cloud.
2. tool and hardware collection, enough to fix or build any invention that pops into my head at the moment.
3. Kindle books, but I keep re-reading them, so they aren't just a collection.
4. pets, when I lived on my Kentucky farm, but my apartment in southern Thailand doesn't allow them. Still, I'm illegally keeping a local jungle bird, an Asian Fairy-bluebird, one of the species that inspired me to move to Thailand.
https://www.flickr.com/photos/129414978@N04/30806857641/in/dateposted-public/