THE single best thing you can do is join a association of rover owners affiliated offroad club in my honest opinion for what its worth. That way you will learn how to drive around the disadvantages of your vehicle while taking great advantage of what it can do. The people there will be of old school with only REAL performance enhancing equipment opposed to lots of pointles bling that has flooded the market of late. A decent set of tyres and some trialling experience will take you furthur than most "Offroaders" at a P&P days. Experience is somthing you can only gain from putting the effort in and there is no cheat unfortunatly. There is no single mod that will make your vehicle go anywhere. Axle lockers is the nearest thing you will get to that combined with a decent set of tyres and some skill you will be far better that the average lifted "kitted" mota. Also by joining a club and being an active member you will keep your vehicle in a roadworthy state which is not usually the case with many playday hacks because it has to be kept in a good condition for each trial event. All that while gaining lots of driving skill, experience and socailize with the best drivers and pickup their knowledge along the way.
IMO articuion is way overated, I know the twist of champ at billing a couple of years ago TD5 lockered up, winches front and rear, sand ladders a full on challenge truck that has bags of articulation still he gets stuck when a bog standard series III and myself drove past through and offered him a tow it was most amusing! Ask Spyderman he was the series driver. Was a case back then of all the gear and completly no idea.