What is best gear for lvl 57 warrior in WOW

The best gear still would be partially heirloom gear, especially the Polished Shoulders of Valor and the Polished Breastplate of Valor. You can also get your hands on the Belt and Wrists of the Valor set (which are dungeon blues) on the AH and are pretty good.

If you are Arms or Fury, the Reforged Truesilver Champion or Bloodied Arcanite Reaper heirlooms are very good. For Protection, go with the Battleworn Thrashblade or Venerable Dal'rend's Sacred Charge in combination with a good shield.

In general, the best items to go for are green-quality items from the AH with the "Of the Bear" or "Of the Beast" suffix if you are DPS, or "Of the Champion" if you are a tank.

In the related link are a few more Plate pieces that are Bind on Equip.