always a good place to start is the Basic's

change all fluids (oil / water / diffs ) (maybe need some cooling looked at - fan / hub / thermostat / fan belts, maybe do some diff breathers while your there...........)
do the brakes - change pads, check rotors & replace if needed - make sure calipers are working
check under dash for loose wiring, and check battery for connections that dont go anywhere (even check previous owners fittings and wiring.... ya never never know............)
check and re grease door hinges (use graphite powder)
check your winch actually works, and make yourself familiar with its wiring and how it works

basically make sure its all working, and everything is safe to use

once you have done that, make a list of "WANTS"
new tyres
Snorkle
bigger Intercooler
bigger Turbo
new Exhaust
LED lights in the back
etc

then "shuffle" this list around using the "have to do for safety first" method

then just play it by ear mate...........