Paper, Pencil, Eraser, Pencil Sharpener, Color Pencils, Aquarelles, Paints, Markers - anything and everything you have and they like to use.
We will start each class with drawing out a flower outline with pencil and marker and then we will mix colors in petals and add more flowers as we move along!
It is better to have a thicker piece of paper that is good for mixed media!

Depending on the age of your child and how independent your child is, I would advise to be on the side and if you can help them set up with paints, water, brushes, color pencils ect. and maybe even draw together with them to have some parent - child bonding experience that would be fantastic! 
I do have to mention that Outschool has a policy that does not allow parents to be on camera while the class is happening, but that does not prevent you to sit on the side and still enjoy your time with your kiddo in this class! Looking forward to meeting you both!