Fir, also known as Douglas Fir, is very inexpensive and common at local home centers. It has a characteristic straight, pronounced grain with a red-brown tint. However, its grain pattern is relatively plain and it does not stain well, so Fir is commonly used when the finished product will be painted. While commonly used for building, this softwood would also be suitable for furniture-making as well.
As the comic George Carlin might say, a shop is mostly just “a place to put your stuff.” The physical aspect of a shop is indeed simply a space of some kind — a garage, a barn, a teepee — that keeps the rain, rust, and robbers away and houses a collection of implements needed to saw, plane, slice, sand, and pound raw wood into useful objects. But just like the difference between a house and a home, what transforms a building full of tools into a comfortable workshop goes beyond the mere physical aspect.