People collect different sorts of things. Some adults might have been so deprived of having a good collection of dolls and toys as children so they still collect those, while others are still so fond of collecting stickers and stationery.
What you collect is dependent on your budget of course! So mugs, stamps and postcards are common items to collect. On the other hand, super rich people could afford to collect vintage cars if they want to! Some are happy with coins. There are not a lot of good coins these days, so collectors go to internet sites to buy and add to their collection.
Good news to coin collectors, morgan silver dollars price guide would be a good site to find out about coin prices. Something like this available online sure is helpful to those coin enthusiasts out there!