This will keep rain away from your shed.
Roof overhang length.
There is a thing called wicking that if on a low enough slope will run up the underside of roofing and possible go up enough to get behind facia so usually without drip edge at least 2 with drip edge even.
You can add 3 to 5 inches to the top.
The roof overhang will be 36 inches at the eaves measured horizontally and 36 inches at the gable ends.
Arid climates receive little rainfall that can cause roof decay and the least danger of decay through.
Overhangs can vary from a few inches to a few feet depending on preference.
That said overhangs can extend as far as 2 without the need for external supports.
Though most overhang regardless because of discrepancies of the facia being straight so they run metal past to let it appear straight.
A typical metal roof overhang may be 2 to 4 inches or even less.
A shed overhang is an easy and effective way to protect your shed.
Some slight overhang is recommended in conjunction with a drip edge flashing to prevent water from getting under the roofing and onto underlying wood.
There is a certain logic in extending the gable overhang further the higher you get as you mention but that complicates the roof and i don t like the look of it.