You can tell what people's hobbies are not only by how much time they spend on them, but also by how much money. It's almost a measure of how much they plan on using the equipment. If you're a serious carpenter, you'll have more than one kind of hammer. I'm going to focus on sports.
I play tennis in running shoes, running shorts, and a t-shirt. I play volleyball (and swim) in board shorts. I recently started wearing a swim cap for swimming. I have 2 pair of goggles, thanks to Camille. One is comfortable but sometimes leaks, so the other (never-leaky) is for races. I am pretty into this triathlon thing now. I bought a bike for $550 then all kinds of accessories (who knows how much money!). I just bought a triathlon wetsuit (not to be confused with a surfing wetsuit) and got to wear it for Saturday's race. I got elastic shoelaces for T2. I have a couple pair of running shoes and a couple pair of race shoes. I've been willing to trade away my money to get these goods.
However, when I do other sports, I'm a little stingier. I didn't buy my own softball bat the last couple times I played. I use my old baseball glove/other equipment to play softball. I did have to get a couple softballs. I use my tennis racket for tennis and racquetball. I have two volleyballs. When I was playing soccer more, though, I bought cleats, shin guards, a ball, socks.
Away from sports: some people spend a lot on their computers or electronics. Others have thousands of dollars worth of (comic) books in their room. Some people trick out their car. Other people spend a lot of money on tools for their cars (which probably saves them money later). Basically, every hobby has some super-specialized equipment that has cheaper (but less technical) substitutes. When people start buying model airplane glue instead of using superglue, they're getting pretty into it. Watch your purchases to figure out what you're into these days.