National Geographic Hobby Rock Tumbler Kit is truly a gift that keeps on giving. We got one last year at Christmas time, and it has been running ever since, except in the coldest months of the year. It is noisy, so you will need to have a place where the sound is not a problem. We run it in the garage (thus the moratorium during the deep cold Minnesota Winter).
There are other rock tumblers out there, and if you want to get serious, you’ll want to shop around and maybe even look at the Vibratory Tumblers, a related technology.
Warning: Figure out a way of disposing of the sludge that does NOT involve putting it down a drain. It will ruin your drains. Dig a hole in the back yard, or make an evaporation system (that’s what we do) so you can throw the dried sludge in the trash.
Expect to buy more rocks, as well as more raw materials. Here are a few examples of what we invested in: