I am chiming in a bit late on this thread, but figured I'd add a couple of tidbits from my soldiering days.
One, if you have concerns about losing exposed items on your pack (i.e. water bottles), secure the item to your pack or person with 550 cord. I was in an airborne unit and we would tie down everything to the point of being compulsive about it.
Two, for pants, you could do worse that get some surplus BDU pants (light weight rip-stop material). I think they were 100% cotton in my day, but more recently have been poly blend. We would wear lightweight year round because if they got wet they would dry faster.
Three, do not succumb to "paralysis by analysis" when it comes to picking gear. After years of having little to no choice regarding the gear available to use, I found the wide ranges of choices in the civilian world dizzying. But I had to remind myself that I humped many a mile with a cheap low-tech pack and issue boots and hundreds of thousands of others have as well. IOW, don't hold out for the perfect gear to get yourself out there.