Suggestions will vary, but the mods/suggestions will all depend on the overall tire size you want, then size for future wheeling, and the type of terrain. You want to do some harder trails, but what's harder in comparison.
First thing, usually is taller aggressive tires. If you go too big at first, you'll spend lots of money to compensate. Stick with 2-3 sizes larger, and much more aggressive. Stay with stock rims or find used ones cheap.
Sami's have short wheelbase, so anything to make those short leafs work, the better. So you could look at swapping the rear leafs up front, adding Jeep CJ rear springs, both with expandable shackles, longer travel shocks (doesn't have to be Ranchos, etc.), and keep it all spring under (for now).
Keep the stock gears in the diffs (you'll need to compensate for the larger tires in the t-case, diffs will come later when you get to 31's or larger tires). Add TT mini-spool to the rear (only $100!!!), add Lock-Right (or other driveway locker) up front. Change your t-case gears to the 4.16 set and it'll lower the 2wd as well as give you creeper gears in low. This compensates for the slight tire change now.
Perform maintenance/tune-up on your engine, change timing belt, add header, free flow exhaust up to 2" dia. add flow through muffler.
Perform maintenance to your axle with new seals. Change all fluids and start off fresh with your time and not previous owners who is probably guessing. Then you've pretty much got a great foundation to start off with. Make necessary mods over the coming year based on how/what you did on the trials.
Folddown windshields, full family cage, cutting of the body, removable doors, etc. all add destinction to your Sami.
Best bet overall is to find other local Sami owners who wheel. Where are you located? Izook has a nice location finder of other Zuki owners.
