Efficient fences and jigs can be built for the shop. People have built Biesemeyer style fences, that are as good as store bought.
A lot depends, on your ability, and tools available to build them with. Time is also a factor.
I think a band saw fence is best bought. A resaw fence, can easily be built.
On my old Delta 14" band saw, I bought a new Jet fence, someone was selling. Great fence! Such a pleasure to use. For resawing up to 4" I use it as is, and add a tall fence to it for thicker resawing. Unclamping, and reclamping a wood fence, for each cut change, gets old, real fast. Been there, done that.
All my jigs are shop built. A lot of them are copies of store sold jigs.
If I was going to do dovetails, I would buy that jig.
Featherboards are easy to make, but when on sale, store bought ones are a good deal.
Make what you can. Buy the rest if you need them.