I think that balsa is unsuitable unless you're Uncle Fester.
I think basswood is preferred, although you could probably use whatever else the hobby shop sells. Check out the pre-scribed wood and see what it is.
My formula would be wood for wood parts and plastic or metal for metal parts, although wood with proper finishing can look like metal.
Look for some scratchbuilding articles or books at the hobbyshop. You might try a craftsman type kit first to see how it's done. Some of them are like scratchbuilding, except a lot of work and thinking has been done for you.