I never did end up buying many stamps. I have a set of Celtic designs given to me as a gift that I use from time to time, but never on something made to sell (or almost never -- I can think of one exception). I think I bought a couple of leaf stamps, and I have a office supply date stamp and a really great set of tiny alphabet stamps that can be set on a plastic holder almost like letterpress type (another gift, and one I have gotten a lot of use out of).
But, like just about any other craft I've tried, there was one thing that kept me from making rubberstamping a significant part of my art/craft making. I took up cross-stitch once, and really enjoyed the meditative aspect, but gave it up soon after. Why? Because I wasn't interested in making someone else's design, and I knew I could like never develop the skills needed to create my own designs without first spending a lot of time working from patterns.
With rubberstamping, though, I soon discovered that it wasn't that difficult to make my own stamps from my own designs. I can't remember where I saw or heard or read about it -- I won't claim it was an original idea, though I suppose it could have been -- but the Internet was relatively young and there wasn't much information to be found. But somewhere, I heard you could cut stamps from white plasitc erasers. So I did it, using an X-acto knife. I think the first thing I ever cut was my original White Raven logo. I still have it.
And though I set stamping aside for a few years while I worked on other things, I eventually came back to it, armed with more knowledge about other forms of printmaking, and with better skills for cutting print blocks that could be put to use cutting stamps, too.
For some people, rubberstamping is one of those scrapbooking crafts that are looked down on as not very original. For me, while I don't want to work from other people's designs, I'm sure as heck not going to look down on someone who isn't interested in making their own. But I see rubberstamping as a kind of small printmaking (though some stamp-making materials come in fairly large sizes and are even sold as printmaking, rather than runnerstamping, elements). And I use it for the same things as I do lino, litho, and intaglio: small art prints and greeting cards, bookmarks, gift tags, and other odds and ends.
The prints tend to be less crisp than printmaking, and I feel they're less precious, but other wise they're no different. The same skills are used to cut your own rubber stamps as to cut any other kind of printmaking surface (though rubber is rather easier to cut than lino, wood, or copper).