I've always had a on-again-off-again relationship with collecting things. Growing up, I was into trading card games (Pokemon and Yu-Gi-Oh), and lighthouses. As I grew out of those, I didn't really do much collecting until I started college. At the time, it was mostly digital games through Steam. When that died off, it was Rubik's cubes, and eventually Homestuck merchandise.
I've also started prepping to have my own physical game collection. I have an idea of the lounge room I'd like to have, and all of my favorite games from my life available to play at any time. I've realized recently that as convenient as digital copies of games are, the preservation of physical copies to play on original hardware is very valuable to me. Most new games I purchase now are physical if I feel they will be important to me. Going back and having to pick up old favorites is a bit more difficult, mainly due to the cost. Unlike a new game, I'm probably not going to be playing these games immediately. They will sit on a shelf until the day I want to try them out again. In addition, I'd like to have the consoles modded to get the best possible picture (RGB mods for retro consoles, backlights for retro handhelds). These additions aren't cheap, so it takes more justification before making the purchase.
As I mentioned Homestuck merch, I have been getting all of the Viz hardcover books (including the Epilogues). They are the main focus of my collection, so I can have the story immortalized with me and available at any time. I have 5 prints framed and hung up, multiple shirts, and plushies. I'm waiting for the day the Homestuck USB drive gets released. I'm happy that the series is still getting merch love, even though the main story has been over for several years now.
Lastly, there are the random knickknacks that get picked up that can't really be categorized. Pre-order bonuses, enamel pins and keychains, fanart, etc. These are a bit new for me, and I'm very particular about them, since I know they will be the 'unique' additions, and as a result shouldn't outnumber the main focused collections.
It's always a boost of dopamine to look up and see the collection you've been working on grow to a point of 'completion'.