Rocks:

This could be something from your back yard, or something you already have at home. The objects you choose can be based on your personal preference or aesthetic. I use this greenish black rock above often because I simply just enjoyed the shape and the color.

Please make sure not to take rocks from public spaces, protected areas, private properties, etc. Please be respectful of nature and your community!

Sand:

Any type of fine sand would be ok. When making a selection, look for these key words: Decorative Sand, Play Sand, Beach Sand, Fish Tank Sand. The color of the sand can be based on your personal preference or aesthetic.