For the prints, use ASA. It has a strong tendency to warp on the base, but as long as the warping is even, it doesn't impact the functionality much. I used 3DXTech Black and Yellow ASA. For the hardware, go with stainless steel. They're on wheels, so they will be exposed to the elements. For the bearings, I would recommend Senston ceramic bearings, available here: https://www.amazon.com/gp/product/B08ZN94S5L/