I have the pro rotary punch from Tandy and it is very useful. It saves a lot of time on straps and such too. Don't waste your money on the cheaper rotary punches though. As someone who just started working with leather a year or so ago, all my tools are from Tandy and they have served me well. If I were doing this as a profession, I might see spending the extra money on professional stamps, but I do this as an advanced hobby and the tools get plenty of use. I have not have any issues with any of the stamps and only one of the tools. (the inexpensive slot punch has to have a massive amount of work to cut properly.)
Another suggestion, since you are just getting started, if you plan to spend more than $500 on tools in the next year, get the wholesale card for $150. You will pay for it in savings with the first purchase. My first purchase was a little over $800 with the price of the card figured in. I saved over $400 that day. In the last year, my savings have been close to $1000, so it is worth it if you plan to spend money there.