I would like to add that one should try to be creative in sourcing of materials. I live quite close to an IKEA and have used cutting boards (Bamboo and oak), placemats (cork), pot stands, picture frames (PE + Acrylic) and shelves as raw material for laser cutting. Now that I have had access to a laser cutter for a while I often spot things that could be used for laser cutting in all kinds of places.
That being said I still haven’t found a good source for thin wood sheets (not plywood). Best thing I found so far is painting palettes.
The primary reason for all of this is that everything that is sold in raw sheets is super expensive here.