Folks the true ghillie suit is for defeating the eyesight of people. A ghillie is a game manager of the Scottish Highlands, and they would wear clothing to blend into the brush so they could hide and catch poachers. Snipers today use them to avoid being seen as they hunt other snipers. They work well when going after turkey, or for dove or waterfowl, but the level you need to break up your image when hunting game is less than vs. a human, as long as you stay motionless or move slow when hunting animals with color vision.
Sorry but a goretex ghillie suit won't work, for the simple reasons that gortex (and other synthetics) and brush makes lots of noise. If you sew gortex strips onto say a jumpsuit, the seams where the thread penetrates the goretex will leak. Ghillie suits simulate foliage, so if you are making a winter one because there is much more brown where you live, fine, but if you are talking snow, you should simply buy snow cammo from a military surplus store. Yes there are folks who make ghillie suits by gluing cloth strips onto clothing with Shoe Goo, but they also tend their suits often, replacing lost "garnish". Replacing goretex on a regular basis is going to be expensive. I prefer to sew the garnish to the garment.
I have made several for turkey hunters, and never had a problem with burlap. Ghillie suits are not for comfort, so you simply make them much larger to allow for the owner to wear something warm and dry under them. I don't use nearly the amount of burlap I would if I was making one for use in the Corps, as it isn't necessary. Further, "classic" ghillie suits have canvas sewn to the front of the legs, waist, and chest, as well as the elbows, to reinforce them, as they are intended mostly for prone shooting or prone hiding positions. When I make one for a turkey hunter, I don't add the canvas, and cover the front as well or better than the back, for the hunter is often shooting from a sitting or kneeling position, and the turkey is being called in from the front.
LD