Use armor kits early
Heavy Armor Kit at skill 180 grants +24 armor on chest, legs, hands, or feet. Those four slots gain +96 armor before the next item drops. The leather comes from kills already on the route. Crafted gear covers missing slots later.
Armor and gear curve
Light Armor Kit at skill 1, Medium at 100, and Heavy at 180. The permanent armor bonus stays on the character through level 60.
Wild Leather covers the level 40–50 leather gap. Wicked Leather carries levels 50–58. Craft the missing slot when the route has not dropped one.
Skinning supplies Leatherworking from beasts you already kill. Turn the leather into kits or gear without a separate farming circuit.
Who benefits
Hunter, Druid, Rogue, and Shaman wear the output and level through beast-heavy zones. Warrior gets little from Leatherworking because plate does not use its strongest crafts. Mining plus Engineering or Blacksmithing fits Warrior better.
Apply the kit in town
Apply each armor kit when the new piece drops. The bonus is permanent and needs no new pull.