Jimny Virgin Requires Advice

A standard Jimny is capable enough for driving around fields and farm tracks.

There are two ways you can go here.

Fit big tyres, a suspension lift, castor corrected arms, extended brake lines, new transfer case etc for about £2k and it will look like the one in the picture. It won't necessarily make it any better for what you are doing, but if you want big tyres without making everything else worse that is what you'll need.

Or fit the biggest tyres you can without needing a lift (215/75 R15s or 195/80 R15 if you want remoulds) and keep everything else as it is for the cost of the tyres.