One camera and one lens. Well that would be my Leica IIIc with a 5cm f/3,5 Elmar.
But I have taken it a step or two further. The bezel is bent back on the Elmar far enough that the f-stops can not be adjusted. The aperture is stuck at f/8. Since the camera is now 60 years old, and I doubt the top shutter speeds are correct, I shoot only Ilford Pan F (ISO 50) in the camera at 1/250 of a second.
So I am one camera, one lens, one f-stop and one film. Very restrictive some might say, but on a sunny day, the set up works fine.