ive read around on few boards now that for people who want to start with one mod and want to get most bang for buck, the general trend is a traction mod over a lift mod
ie start with a good set of tyres - 31's easy for a pathy
or maybe a locker
however with all the stuff we know here you can do suspension and body lifts fairly cheaply so that might be the way to start with small outlay.
depends what you rather first
i say good tyres (cooper, bridgestone or even kumho mud terrains!!!!!!!) then suspension/body lift, then a locker for the rear diff