• Breastplate requires 260 Leatherworking, the pattern is sold by Masat T'andr, the recipe is limited and the spawn time is quite long, you're gonna need some friends to help sniping it.
• Leggings requires 270 Leatherworking , the pattern drops quite easily from the Murk Worms that lurk in Sunken Temple, usually you won't kill many of these during ST runs, if you are intrested in this recipe, you must convince your party to help you clear them up hoping for the drop.
• Gauntlets requires 280 Leatherworking, the pattern is taught by Peter Galen (A) / Thorkaf Dragoneye (H).

Crafting the whole set requires

• 60 Rugged Leather
• 80 Green Dragonscale (!!!)
• 1 Cured Rugged Hide
• 5 Rune Thread

With the exception of Peter Galen (which is in Azshara) and Thorkaf Dragoneye (which is in the Badlands) all the patterns are retrieved in Swamp of Sorrows/Sunken Temple, which is where you will more likely farm the Green Dragonscales you will need, although there are plenty of Green Dragonkins around the world.

This, along with Blue Dragon Mail and Black Dragon Mail are the only pre-TBC Mail sets you can craft with Leatherworking, curiously, no piece in these sets needs Dragonscale Leatherworking.