The zone you start in isn't under your control, in as much as it's pre-selected for you based on your race. But for leveling purposes we want to make scaling work for us as much as possible. That means sticking to the lower level zones. Even though scaling will increase the level of the quests and mobs in those zones, the layout and design of them is built for a player with no mount. So you'll blaze through them and gain more exp/hour than higher level zones which assume you DO have a mount.
And more people are buying gold with the expansion turnover; token prices fell from around 207,000 gold in mid-July to around 185,000 gold right before Battle for Azeroth launched. They’ve fallen to around 150,000 gold in the first few days of the expansion. That’s still five times as much as they were worth two years ago, but it’s a 25 percent drop from where they once were. This means that significantly more people are interested in buying gold now than a few weeks ago.
For your tank... I'm assuming you meant which race should you be, not which class, since you seem to want to be a warrior! Well, if you were Horde side I'd recommend Tauren for the health buff. But honestly, I *never* pick a race based on the racial features - only based on the flavor. If you are going Alliance side, I am quite partial to dwarf warriors myself but pick whatever seems most fun to you!
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Heirlooms. At the bare minimum you make sure all the armor pieces upgraded to 110, since this is the lion's share of your experience increase. Neck and Ring upgrades are secondary, but still important due to being able to enchant them. Trinkets can't be enchanted, but you'll want them at max as well, if only to save time by not having to worry about replacing them as you level.
At Level 78, you unlock the stat Mastery, which increases your Shadow damage. When you unlock this stat you should switch your level 56 talent from All Will Serve to Clawing Shadows, as it benefits more from the Mastery. The mechanical change when using Clawing Shadows is that you will be able to pop Festering Wounds from a distance. If you want to attack multiple targets with Clawing Shadows using Death and Decay's cleave effect, make sure you play the Death and Decay below your own feet instead of the target.
Something to keep in mind as well is that this will make enchanting materials more valuable, since it is likely most players will now simply scrap their boe greens instead of getting them disenchanted. Also redundant dungeon/raid gear can be scrapped rather than traded to the (guild) enchanter in the run. Less stuff gets disenchanted, meaning there will be less ecnhanting materials, meaning their value will rise. All the more reason to DE rather than scrap as an ecnhanter.