The basic consumables that any player should probably stock up on are food, drinks, potions, and bandages. In Battlegrounds, players can go on the cheap and rely on the Restoration Power-up that randomly spawns in key points all over the map. In Arenas, players can use Healthstones, Conjured Manna Biscuits, bandages, and the various mage gems. Because encounters are very fast-paced, it's sometimes difficult to catch your breath and get out of combat long enough to eat or drink. This makes Health and Mana Potions good ways to extend your longevity in battles. Fortunately, the folks in Arathi Basin and Warsong Gulch recognize your efforts and send you lovely care packages as you gain more reputation with the associated factions.
The care packages are rewards from quests that become available upon reaching Friendly, Honored, and Revered reputations, so make sure to drop by the Arathi Highlands or the Morshan Ramparts (or Silverwing Hold) every now and then. Each care package contains a stack of rations that restore health and mana, as well as a stack of bandages. These consumables are Battleground-specific, such as Arathi Basin Enriched Rations or Warsong Gulch Runecloth Bandages. On the other hand, supply officers for the Frostwolf Clan and the Stormpike Guard of Alterac Valley sell food, drinks and bandages that may be used outside of the Battlegrounds, as well as Health and Mana Potions that can be used in any of the four Battlegrounds.