Nice tidy zook you've got there... Should be OK off road with those A/Ts on it...
Although, First mods I would consider it a set of mud terrain tyres....
I would recommend either the Insa Turbo Saharas (my old tyres)
or Kumho KL-71s (currently tyres)
both are well behaved on and off road...
After that I would maybe look at 2" lift and some wheel spacers... I find that to be a perfect initial setup...
will give decent amount of ground clearance, and increased stability
Avoid extended shackles like the plague. The best value way to lift 2" is add-a-leaf...
Should cost roughly £100 to lift
Wheel spacers tend to go on ebay for around £50
Sets of tyres vary on type and condition
I got my current set of 5 for £170
I got the last set of 4 for £90!!!
so fifthty takes the biscuit. Lovely car juat to take a moment and smell the roses, but in my case sometimes theres a burning plastic smell have put this down to a crank shaft oil seal. Like peeps advice on some slight mods for her would like to keep as much of it looking as standard. To my surprise or as far as the eye can tell there is no rot no any of the arches. Was a bit concered about the throttle pedal that was hanging on by a thread, the original metal around the stud had rotted away so quick repair for now with reapir washes m10 and nut. 
but got to replace the original fuel filter 
so that might help. was looking at vitara conversion.
not sure if the spi ones had it but on the carbed models there is an idle up to compensate for extra power drain when you turn on the lights and heaters etc. These sometimes play up so that could be part of your problem? If it has one of course? If so just dissconnect it as its not really needed.
