It is a good sign that the tach moves when revving the engine. That means the needle was probably removed at some point and put back on incorrectly. With the engine off, take the plastic lens off the cluster then simply pull the needle off with your fingers then press it back on while aligning it to zero.
I had the same issue when I got my truck. Although it was clear my gauges had been messed with as there was aftermarket gauge faces on it. The gauge faces on yours are original.