Since you bought the truck new, selling it will probably lose you a lot of money. I would have suggested Certified Pre-Owned to save several thousand dollars on the purchase price, but you can't really do much about that now.
But really, trying to get better FE in a pickup without major aerodynamic and/or drive train changes is pretty difficult. Buy a cheap little runabout to drive to work, and use the truck only when you have to. 1988-2000 Honda Civics are like go-karts to drive and non-Si models get good fuel economy. Parts are cheap as can be. Mine's for sale.
Block the grille as much as it'll put up with. Add a deep air dam up front and build an aerodynamic topper. Skirt over the wheel wells- you may be able to attach skirts in factory holes.
Make your truck look like this...
