Hi, for economy you would need to choose a Low Drag aircraft, so that the Thrust is most efficiently used... Hence a low fuel consumption.
This seems to point to a High L/D ratio, which is only available to Motor Gliders or powered Sailplanes, which achieve 30:1 and 45:1 respectively.
A typical Cessna has about 15:1 in comparison.
If you factor in the cost of hangerage, the detachable wings make for easy storage in a trailer. Also the cost of an annual service can be considerably less for Gliders, as there are so many less bits to go wrong.