You may add a few plants to fine-tune your Ghillie suit's appearance, but the bulk of the suit is made beforehand, quite laboriously. The camouflage of the suit consists of many individual strips of fabric that need to be sewn, by hand, to the garment at the core. These strips are what breaks up the human outline and turns the suit into what resembles a pile of ground of the appropriate type.

There's absolutely no way you can make a Ghillie suit crafted for one type of setting into one suited for an entirely different one just by gathering up local materials. If it were that easy, everybody would have excellent, terrain-specific camouflage, pretty much all the time. That just doesn't happen.