Gearing rogue 10k-15kish

[Freakish]

Get the highest damage weapon you can for primary. This affects your backstab max damage.
If you have a high level friend who is fronting this cost, see if he'll help you do epic. This is the biggest damage increase, and surprisingly simple for rogues.
Other primary options are Crystalline Spear and Serpents Tooth. A cheap(ish) offhand is Crystalline Short Sword, or look at weapons. Anything above a .5 ratio will cost quite a bundle.