I've wanted giantstalker shoulders ever since vanilla, so I started with that (recolored), and kind of worked outward from there - the one problem with these shoulders is that they have a somewhat muted color scheme (as compared to some of the newer stuff from cata and wotlk), and after a lot of trial and error with various cheap AH bits, I ended up gathering the recolored Giantstalker gloves, belt and boots as well, since nothing else seemed to match the shoulders.
But was determined to go outside of the giantstalker recolor set for the rest of it. After some more tinkering I found the counterfeit mail (aka green lowbie cata quest chainmail) to be a surprisingly nice match, and used that for the helm, chest and leggings. The cloak came from a BRD quest (Maxwell's Cloak).
For a gun (and it has to be a gun after all), nothing matched half so well as the Alliance Vanguard sawed off shotgun, and since I was already up to revered with them, that was an easy decision!
Her melee weapon was a bit tougher - everything I could find was either the wrong color, wrong shape, or else it overshadowed her other items. Finally I discovered the Shen'dralar Trident, an obscure polearm from a Dire Maul quest that I probably never would have bothered with under different circumstances, but it had the right colors and a bit of a martial look to go with her shoulders without overshadowing them, so... I had my last piece.
The funny thing is that Gunhilde has had a green theme ever since she tamed a jade scorpid back at lvl 22, so it was pure serendipity that she ended up with this theme (ditto for the tabard - and no I didn't choose the guild based on it).

Tabard / helm hidden
No tabard / helm visible