I can understand being new to the ecomodding society you don't want to do extreme mods to your cars quite yet, ex boat tail. Normally where people start with aero mods are air dams, grill blocks there easy to do can be made to look factory very easily and are cheap.
Also agree with above knowledge is power or in this case fuel economy the more you know about driving techniques and how your car is reacting to it would be the best way to maximize fuel economy. If you already have a fast car implementing tips to your dd would be best that way when you get the urge to drive fast you switch cars =) Hers our list of tips to maximize economy
100+ Hypermiling / ecodriving tips & tactics for better mpg - EcoModder.com
As far as the jeep what kind of lift and tire size always been into wheelin myself just never had the money to justify gettin a rig