Here is a general progression of chest pieces for a DPS Death Knight in Northrend for World of Warcraft.

Starting out in Borean Tundra, you’ll want to focus on obtaining the Battle Leader’s Breastplate. This will carry you for three levels until you can hit Dragonblight for the Chestplate of the Ruby Champion.

Your first opportunity to pick up a rare item will be at level 76 with the Kalu’ak. If you’ve completed all of the quests for this faction in at least two out of the three zones where Kalu’ak quests exist, you should have no trouble reaching honored.

You can then run Gundrak for the Forlorn Breastplate of War from Moorabi, or hold off until 80 and complete the quest “Whatever it Takes!” in the Halls of Lightning. Although you can pick up this quest at level 77, you’re more likely to find a heroic HoL group at 80, then you are a regular HoL group at 77.

• Level 68 Mightstone Breastplate (1436)
  Obtained by: Quest Reward – Bury Those Cockroaches! (Borean Tundra)
• Level 68 Battle Leader’s Breastplate (1601)
  Obtained by: Quest Reward – What the Cold Wind Brings… (Borean Tundra)
• Level 71 Chestplate of the Ruby Champion (1815)
  Obtained by: Quest Reward – On Ruby Wings (Dragonblight)
• Level 73 Carapace of the Fallen (1932)
  Obtained by: Quest Reward – A Minor Substitution (Grizzly Hills)
• Level 74 Chestplate of the Altar (1971)
  Obtained by: Quest Reward – Precious Elemental Fluids (Zul’Drak)
• Level 75 Links of the Terrified Deity (2001)
  Obtained by: Quest Reward – Convocation at Zol’Heb (Zul’Drak)
• Level 76 Whalebone Carapace (2194)
  Obtained by: The Kalu’ak (Honored)
• Level 76 Forlorn Breastplate of War (2413)
  Obtained by: Moorabi (Gundrak)
• Level 77 Breastplate of Jagged Stone (2812)
  Obtained by: Quest Reward – Whatever it Takes! (Halls of Lightning)

Prices and links provided by Wowhead. Gear score provided by Loot Rank (based on the PvE Death Knight template).