Some basic conceptual examples were given before, but you may need some more concrete examples of what item collecting looks like in the various mediums and the variety of forms it can take. Should you wish to incorporate it in any of your experiences.
Within games, video games, board games and so on, I’d be hard-pressed to name a game that doesn’t have some form of item collection mechanic in it. Survival games, RPGs, strategy base-building, CCGs (collectable card games), and even FPS (first-person shooter) games have some form of item collecting in them.
If we look at games like Pokémon, we’re collecting creatures to do battle with. Minecraft we’re collecting everything in that world to progress further, resources to build, explore and so on. World of Warcraft, EVE, and Fortnite, all have gear collection and resource collection so that more dangerous areas can be explored, and more powerful enemies can be challenged. And then games like Valheim, V Rising, and ARK, all have you collecting a variety of items to survive and gain power. The list is genuinely endless.
In the physical world, we have games like Magic the Gathering, Yui-Gi-Oh, and Warhammer, all of these are about collecting things so that you can keep playing. Even postage stamp collecting, model trains, planes, and more.
And then as I mentioned in the real-life world, I certainly collect books, and at one point I collected DVDs. I know people who collect shoes, and clothes. Some of us collect knowledge, some organisations collect information. And we are all obsessed with collecting money of course. Item collection is everywhere.