If possible, avoid purchasing Gear from the Auction House - Ideally, you should be able to achieve level 60 without buying anything from the Auction House. This way you will save Gold, but possibly make leveling a bit harder for yourself. If you badly require an Item upgrade, and the suitable Item is available on the Auction House for a low enough price - buy it, but only if you think that the investment will pay for itself in one way or another (the main exceptions to the Auction House ban Rule are Weapons and Wands, as they make leveling much faster, and pay for themselves by allowing you to chain-kill more mobs without Eating and Drinking, which saves Gold and time).
Monstrous Plaguebats (market GREEN on the map) - These are larger cousins of the normal Plaguebats. They occupy northern parts of the Eastern Plaguelands and drop Vendor Trash Items (Evil Bat Eye, Bat Ear, Sleek Bat Pelt, and Large Bat Fang), Wicked Claws (used in Leatherworking and Blacksmithing Recipes), and maybe some 16 Slot Bags. These can also be skinned for Rugged Leather, Thick Leather, Thick Hide, and Rugged Hide, so Skinning Profession is recommended for Farming them. Monstrous Plague bats have access to the Sonic Burst ability, which is a 10-second Silence, so they are not a good choice for Spellcasting Classes. Recommended Level - 56+.
WoW Classic seeks to recreate the "vanilla WoW" experience—that is, WoW as it existed before a series of seven game-altering major expansion packs from 2007's The Burning Crusade to 2018's Battle for Azeroth. To achieve this, Blizzard has rebuilt the game based on archived data from back in 2005 and 2006 (patch 1.12 is the goalpost—the current game is on patch 8.1.5). The company has committed to meticulously presenting the experience exactly as it was back then—warts and all—with only a small number of unavoidable or critical changes.