Try using your phone camera before you buy anything extra. You will likely find you're not really going to watch those movies anyway. :) I put one on mine, and watched the first couple cause I thought it would be neat. But I watched a couple, but never did really get enthused with it.
An older GoPro can be had for not a lot of money. No sense in spending big bucks for the latest and greatest until you decide if you'll stick with it. Used ones are common, because people thought the same thing as you, and found they didn't use it much after all. :) Check Facebook marketplace for a good place to start.