Yes, wood and some of us don’t have anything set up to make our own but there are web sites that you may know of who sell G scale.
Different wood/s, you know the good stuff!
Toad
Enquiring minds? I would like to build some items but Home Depot doesn’t have it.
for roughly correct 2x10’s x 8ft, I go to the fabrics and crafts section of walmart. For other timbers I got a small table saw for Lowes at half price on clearance sale.