Get your item level as high as possible. Having the best gear is always going to help you when clearing content, so upgrading your individual pieces of armor will be important in the first few days after the expansion’s release. If you’re looking to get ready for Uldir, then you’ll want to be around item level 350 by the time that raid is released on Sept. 4.
Now that you have these addons, it is time to set them up properly to be used as effectively as possible. With the first addon listed, Auctionator, you will get three additional tabs when you open up the auction house: buy, sell, and more. Buy and sell are easy to follow and read, the primary reason why this addon is the top choice and listed as number 1. You can easily set how much to buy or sell, ranging from 1 individual object to stacks of the same good. The most important way to search is by price per individual item. This will avoid both overpaying and underselling, since you can see what one item in a stack is worth compared to what it is worth when being sold on its own. The "more" feature provides an easy-to-follow window of all your auctions up and the details associated with your auction, such as price and time left, in a nice color coded fashion. Without this addon, you will be severely crippled compared to anyone using this efficiently. If you are afraid of addons for security reasons, the rest can be ignored as long as you have Auctionator!
Enchanting is a crafting profession that allows you to enchant gear with stat increases. It also allows you to disenchant gear for crafting materials. Enchanting uses crafting materials that can only be obtained from disenchanting gear. This means the only source is either crafting yourself or buying from other players. As the profession mostly revolves around stat increases only the legion recipes are relevant. Enchanting is also a great source of obliterum. The other ways to make gold with the profession is crafting and selling enchants and doing the enchanting shuffle.
Battle for Azeroth’s War Mode puts you into PvP mode and grants you 10 percent extra experience. But since the two factions will mostly level in separate zones entirely, you should almost definitely have this on when you’re leveling. That said, if you start getting killed by random PvP players consistently, stop using it. Although 10 percent is nice, it’s not worth dying every few minutes for.
The downside is that War Mode will make you vulnerable to other players, which means you might be killed more often. Whether it’s worthwhile will depend on the zones you’re visiting and how active the other faction is on your server cluster. Heavily populated realms usually mean more players on both sides, and more conflict, but on quieter realms, you may rarely run across an enemy.
101+ At this point you'll start taking a penalty on quest/bonus objective experience for every level past 100. Treasures, however, remain worth their full value all the way through level 105, at which point they'll be worth something like 15% less, and then another 15% more when you ding 106. I recommend that you stop questing/gathering entirely, and collect all the treasures you can stomach, only avoiding any annoying to reach ones inside caves or behind elites/rares(where scaling does bizarro things).
Make sure you have the two Flight-Path toys purchased, as this can save you time. It won't have EVERY flight path, but will have major locations for faster travel if you need to switch zones entirely(which you will). If you buy the toys on one faction, it unlocks for the other faction as well. So don't spend double the gold! These toys can be found at the heirloom vendor(Undercity for Horde, Ironforge for Alliance)

From “The Burning Crusade” expansion, weapons like Klinge der Zauberei, Die Nachtklinge and recipes for different weapons are really valuable. The best example is Pläne: Teufelsstahlangschwert, worth 500.000+ Gold. These items are World Drops, you can find them in all raids and dungeons. I don’t know any Open World Drops, but that does not mean there are none. Another great transmog source are world bosses and rare spawns on Outland.