I generally shift 1 at a time, harder or easier as terrain changes.
The front chainrings are like "High" and "Low" range.
Lots of short hills near me, so I am in the small chainring most of the time.
i shift to the large ring if I have extended time on flat roads or longer downhills.
I have no idea which gears overlap, not really relevant when riding.
Whichever gear keeps my RPM in the 85 - 95 range