As one of the previous posters mentioned, you can go deep down the rabbit hole in term of cost. I went in on a nice APS-C (crop sensor) Canon with a couple of nice lenses and often found that I preferred my iPhone photos (I like the focus sharp and it's easy to get things out of focus if you've a large aperture). Granted, many of these are of moving family on moving rides, but still....
I've doubled down and love my L-lenses on my full frame camera and treasure the results, but $$$
Don't be surprised if you find that you iPhone is still your go-to.
To be honest for a lot of people an iPhone is probably their best bet for a camera. Especially if most of their photos are taken in daylight or reasonably bright light. The real advantage of the higher end cameras is in catching the difficult shots, but the trade off is the user has to commit to learning how to use the camera... Otherwise it wouldn't matter if you gave some people a Nikon D4 and the most expensive lens in the lineup... if the user wasn't willing to spend some time learning the camera the shots will be no better than shots from an iPhone and quite possibly worse.