The trivial level on this armor is above 116 but probably not much higher. That's what I'm at and I've made 2 belts, gorget, leggings and boots and only failed 2 out of 7 attempts. Probably around 125 or so.
The recipe book is sold by the leather pattern merchants in Kelethin. Basically, its a regular studded leather recipe but use Sabertooth hides and Mithril Studs and then add an Imbued Emerald.
All the Imbued Studded Leather items trivial at 122. And you also need to add Oak Bark Tannin to the above recipie; this is brewed (trivial around 100) from Oak Bark, which is a ground spawn in Butcherblock Mountains, or Foraged in Warsliks Woods and Kithicor Forest.