Don't stress over stamping, we all had to start somewhere and all it takes is practice. While the same can be said about carving there is a lot more subtlety involved. I always thought I'd never bother (too hard) but eventually wondered if I could do it. Yes, I can, BUT I've got a long way to go, which doesn't matter as I only do it for myself.
As for buying a machine, my suggestion would be no, at this stage, based on everything you've said. I started by buying used machines I picked up at good prices but I really had little idea of what I was doing! If you do lots of reading on here and study the various projects people make it will give you a better understanding of machine capabilities and should help you decide which machine should best suit your needs. IF you finally decide you need one.
I forgot to mention, there are lots and lots and lots of videos on youtube about stamping, carving, sewing etc etc. I have spent many hours watching them and learned a lot.