This is my Automatic Zen Garden, made using accessible parts from the maker's supply page and a small amount of sand (100g). I got my sand from Amazon by simply searching for "craft sand." There are a lot of types/color choices, and I'm sure most will work fine for this model.

The assembly for this model is very simple:

Start with the base part, ignoring the very smallest gear install the gears in order of size (large to small) use the provided images if this isnt clear. Then place the smallest gear onto the drive shaft of the TT motor and make sure it's securely on. Feed the USB cable through the hole in the side of the base and locate the thin pole sticking up in the bay for the motor. The TT motor has 2 holes that go all the way through it. Align the pole on the base with the right hole in the motor and let the teeth in the small gear fit between the teeth in the large gear next to it. Then place the top part onto the base unit. Take the rake and align it with the square hole in the last gear. You should be able to see it through the hole in the top part. Make sure this part is fixed securely. After this, pour in 100g of sand of your choice. Plug in the USB cable and let the Automatic Zen Garden do the rest.