Which traits?
Backstab is an ability that replaces you first ability (auto-attack) when you’re in Stealth. Just watch how your toolbar changes once you enter Stealth (via Cloak and Dagger mostly).
As for traits, at this point is barely matters but you can’t go wrong with points in Critical Strikes, which are the basis for all Backstab builds.
Early on I’d invest the other 10 points into Deadly Arts as the early traits are actually quite good.
Dee Jay is spot on. In your early levels, DA is your best choice for your traits. If you have a dagger equipped in your main hand, you’ll be able to backstab.
Practice stealing, hitting CnD (Cloak and Dagger), and positioning yourself behind your target. Once your stealthed and behind your target then you can get off a backstab. Have fun!
Ferg Crossing