All equipment modifications aside, STILL, the most cost effective and useful off road modification comes with good driver training, and/or experience. I've seen it time and time again where a fully knitted out off road beast is bogged to the axles and I drive around them in my soft roader on S/T tyres.
As a military member wiith over 20 years driving in pretty much every condition you can imagine, I can say unequivocally that a poor driver in a great vehicle will go nowhere, whereas, a good driver, who assesses the obstacle, selects the right gear (when appropriate), and attacks (sorry for the aggressive words here - it's in my nature) the obstacle at the correct speed, picking a pre-selected line as appropriate for the vehicle, can go pretty much anywhere in a standard vehicle, with average tyres.
Go get yourself some training mate. Then decide what mods you need. All good advice on here about suspension and tyre mods from very knowledgeable people, but I guarantee they are all moderate to very experienced drivers first.

