Like pricking irons, stitching chisels' main purpose is to set up your stitch placement on your work.
Diamond chisels are the stitching hole maker of choice for most new leather workers. They are strong, easy to use, and affordable. Ensure you don't buy a diamond chisel that is black. The black ones are actually covered in a coating which makes them difficult to go in and out if leather.
This is a list of tools I'd recommend for a beginner leather worker. This list is far from exhaustive but it should get you up and running for a fairly affordable price and let you figure out if leather craft is for you.
Check out my video on how to get started in leather work here: https://youtu.be/ZIgxsMtjE8Q
Follow me on YouTube and Instagram or you can check out my website where I post additional info to all my videos and have downloadable free leather craft patterns.