You'll also need to choose among electric, diesel and steam engines in G scale, No. 1 gauge. It's stainless steel and a very, very special quality of plastics. A lot of the running gear and parts are stainless steel or brass. Some parts may even be nylon. A useful resource for information on equipment is Center Lane Hobbies in Hyannis behind the Cape Cod Mall.
Some garden railways concentrate on natural features, while others include a variety of buildings.
Martin's layout tends toward the former. I fully expect to add to it and make a bit of a village in one area. Model railroaders are also in the construction business, and Martin is no exception. He uses wire lath to create sheer rock cliffs and viaducts. To frame buildings, he uses concrete sand mixed in small batches and uses a putty knife to butter it onto a closeknit wire frame.