Depends on water depth. Mine is usually set to 70’ feet. I always adjust my gain down to 70-75 because in auto it always seems up around 80 which washes out the returns in my opinion.
These setting have worked for me from 5-20 FOW as long as fish are in the upper 1/3 of the water column.
Do you have Garmin’s mount or another style? Perspective would not be that great if you don’t have infinite adjustment. Hence some of the complaints you read online. I’m always adjusting my “tilt” to get the best view of where the fish are.