HI
@luwaimn, I am driving with just a stock Prado, do not have skid plates or anything really. Looking now the engine area below, I would say skid plates definitely makes sense. Low liners definitely no go, they'll be lost in first drive.
If you wish to have a sturdy front, steel bumper makes sense. It will increase weight a bit, maybe 30 kg +. I don't think this additional weight will impact your car performance too much though, hardly at all, if you have 4,0 l engine. It has plenty of power.
@Luca Palanca Falsini has in his Fortuner modified steel bumper and looks cool and certainly will not get bent easily.
As @Chaitanya D said, speed and approach angle for dunes makes big difference. I learn that hard way, having small dents in my front now.
See u on sand...