I usually leave my WB set to AWB (automatic white balance), auto focus, and camera set to manual mode. My eye sight sucks and I can’t see for shit so manually focusing for me doesnt happen too much. I will do the “focus, recompose” method of auto focusing on a subject, switching to MF to keep that part in focus. But doing that with a super shallow depth of field can sometimes cause your subject to become out of focus if you move too much.
Best way to learn is on manual mode, try it out sometime. Set your ISO to 100 or 200, aperture to 1.8, then just use the light meter in the view finder to adjust your shutter speed. Its super easy once you do it a few times.