I had a rock hounding phase in my life ... It was something fun to do with the family and we have a lot of interesting rocks in BC.

I built my own rock tumbler using some wood, hardware store bits, and an old geared DC motor... I also used commercial rock tumblers. Those worked better ;)

It takes a really long time to tumble rocks, you have to go through the grits like a week or two at a time, and they sort of come out without a lot of character. Hand polishing them (with power grinders and polishers) is a lot more satisfying and you can make them into your own. That does require more equipment though.