If I'm going to drive on a public road then I need a
speedometer, and an odometer helps for navigation.
 
My 1965 Chevy has a bare minimum:  Engine-temp and
Oil-press warning lights and a fuel gauge. 

My 1983 VW has tach, water-temp, voltmeter 
and oil-temp gauges. 
 
If I had a turbo car, I'd want a vacuum manifold/boost
gauge.  An oil pressure gauge is a nice, reassuring
gauge to look at.  If my car was air cooled, then I
would substitute a cyl-head-temp gauge for the water-temp
gauge.
 
A few years ago, I looked at the Audi Quattro Si Coupe
that Bobby Unser used to win the 1986 Pikes Peak Hill Climb.
The gauge layout, from left to right, top to bottom was:
 
----------------------------------
 
speedometer
 
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fuel                  tranny
press                 temp
 
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differential           water
temp                   temp
 
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big orange             tach
oil-press
warning light
 
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oil-temp               boost
 
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oil-press
 
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