The desert kit supplement is pretty good, altough I've heard that they aren't issuing softee jackets at the moment as these are only winter issue. If you're going to be out there for some time, take some warm kit (or have someone ready to post it) - although it is baking at the moment, it will get cold later in the year.
A GPS was very useful - the maps you get issued are all large scale (1:100,000) and its pretty hard to work out exact grids of where you are. The issue spot maps are much better, but even then GPS is useful. Set it up to give you MGRS grids, and base datum of WGS 84.
Regarding webbing, depends what you are doing, but my assault vest was very useful. Even if you're not in a AI/Mech Bn you'll probably be working a lot out of the back of snatches or Wolfs, and there's not much room in the new ones as they've put a bloody big aircon unit in them. Some way of carrying UGL rounds / Minimi link if you're that way inclined.