I do not recommend going for TBC, although I remember Hellfire peninsula to be decent, everything else is rather slow. Instead go for WotLK, Borean Thundra gets you levelled very fast, and then you can head straight for Icecrown at 67, which is also insanely fast, although admittedly has a few elite quests. You can go to Sholazar Basin alternatively. 2 zones should get you 60-80 no problem.
Bags: This SHOULD be a no-brainer. The cheap-o version are Netherweave bags, but if you have the gold I recommend you get the largest bags you can afford, since it means you won't have to stop to clean them out as often. In fact, if you have an excess of gold, it's probably not even worth your time to stop and loot mobs that aren't quest objectives. This seems like a small thing, but over the course of 100+ levels, all those clicks to loot add up.
Leatherworking is a crafting profession that uses various leathers obtained from skinning to craft leather and mail armor. You can make gold shuffling leather into enchanting materials through the rank 3 bracer recipes. Battlebound for Stormscale and Warhide for Stonehide Leather. The other main market for Leatherworking is crafting the item level 850 gear. I find that both Dreadleather and Gravenscale gear sells very well.
Note that these general principles do not apply to blue or purple items. If you are a first-time player, there is absolutely no reason to purchase these items. None. Sub-80 rare and epic items are only for the alts or twinks of established players that have money to waste (because that's what it is) by showing off their Staff of Jordan (or whatever). Blues and purples are completely cost-ineffective for first-time characters. Within a few levels, you will find green gear that is roughly comparable, or you'll get better blues from instance runs at the same level. So, do not buy these items, under any circumstances, if you are a first-time character (no matter how cool they look). And even if you're reasonably well-off financially, think twice. This is especially true as your character gets closer to levels 58 and 68. Even the most basic quest-reward gear in Outland will have substantially better stats than anything you can buy off the AH for a level 56 character. The same is true of Northrend gear at level 68 vis-a-vis the stuff you'll get in Outland at level 68. As such, smart players stop making AH gear purchases by about level 54 or so, and then just gut it out until level 58. The same is true at levels 64-68. Within the first several quests in Hellfire and/or Northrend you'll have replaced half of your gear in any case, guaranteed.
Obtaining Items from the Black Market Auction House Everything about the Black Market Auction House, including unique items for sale, how to place bids, and where to find the Auction House. Professions in Battle for Azeroth Professions in Battle for Azeroth, the next WoW expansion after Legion, have received a significant update, with many new recipes as well as a significant skill squish. In this overview, we'll highlight the major recipes, reagents, and useful items each profession offers. Obtaining Blizzard Shop and BlizzCon Vanity Items How to purchase and collect all of the mounts and pets from the in-game Blizzard Shop and special promotional events like BlizzCon. Obtaining All the WoW Trading Card Game Items Learn all about the quirky Trading Card Game items, from spectral mounts to weather machines, as well as look-alike items that are easier to obtain.