I would purchase a secondary polish, the grit works just fine. The instructions in the booklet for "tumble time" are also incorrect. The tumbler itself is great. 3lb tumblers are standard so for beginners it's great.
My boys love rocks! We got the hobby sized rock tumbler which comes with 4 polishing grits to polish up your rocks. We are studying geology right now and went rock hunting today. I had to order more grit to polish our new rocks. It does take a few weeks to complete the four stages of the polishing process and it is a bit loud. We will be putting it in the garage this time around. Aside from the noise, it's a great tumbler for polishing your rocks.
I volunteer with Big Brothers Big Sisters and my Little enjoys science. This may be a great gift for him.