Tank ruts, swamps that go uphill, giant ant mounds, all set against the scenic back drop of the magical metropolis of Petersville. Ahh the memories....
You can, or could at least, get away with a little after market kit, especially in the field. In garrison there is little room for creativity, or need for it really. But in the field staff is normally a little more accepting of stuff. Just make sure it's not too obvious.
Socks, long underwear, I had some different mitts for the field. I also used an NBC bag most of the time, many did not and no one ever said anything. Just don't show up in the field with TONS of Gucci kit and you should be ok.
Also, spend the money to get a) really good easy on the knees running shoes, and b) the best insoles for your boots money can buy.