Enchants. I honestly wasn't 100% certain which enchants were best, since scaling has screwed up a lot of things. IMO, just pick the enchant for each armor slot that has the highest bonus without level restrictions. The exception is that you'll definitely want Mark of the Hidden Satyr for your neck piece, and probably Elemental Force for your weapon. Both of these proc consistently and strongly across all levels.
There is a constant market for transmutations. If you are capable of doing these, you can charge an upcharge on each of those transmutes. A player who logs on his/her character each day, and sticks to it, can generate a significant subsidiary revenue scheme through transmutes. Likewise, if you have a transmute that allows you to transmute a lower value element (such as Earth) into a high-priced one (like Water or Fire), you can make a cool 15-20 profit every day by simply doing your transmutes.
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.

As you're leveling, I generally recommend you just follow the natural flow of the progression through each zone. They're laid out fairly reasonably. But don't be afraid to hop around, especially if you're near a quest objective. You shouldn't actually need ALL of the zones listed to reach 62. Pick the ones you like best. It's much more important to simply be as focused as possible and flow from one quest to the next.

The cloak is nice because you only need one of these instead of the previous cloak versions since the primary stat changes depending on the class it is used on. The on use trinkets for versatility, haste, or critical strike could be very strong if used together by numerous party members with the same trinket. Finally, the threat reducing trinket could be useful for solo levelers in dungeons with newer, non-heirloom geared tanks in order to not pull threat on some larger packs of enemies.
Similar problems have risen in the leveling system, which automatically scales to the player’s level and equipment. For the most part, you’ll vaporize enemies more quickly as you gain power, but there are some weird dips. Many players complained they felt less powerful at level 119 than at level 110, a problem I experienced myself. And world PvP remains a strange and whacky world where level and class balance issues make wins and losses feel destined instead of earned.
Some add-ons come with a built in application that will setup the add-on automatically for you without any need to do the setup manually. You will just need to specify where you downloaded the add-on and the application will set it up for you. A good example of such hands free add-ons is Nubun Alliance Guide. The in-game mod offered comes with its own installer that will set it up for you as shown in the picture:

Some people have made arguments that quest blues can sometimes be more powerful than heirlooms, especially with sockets. I'm not convinced. The simple fact that you never have to even look at quest rewards will save a non-insignificant amount of time over the course of leveling. Also of consideration is the value of enchanted gear never having to be re-enchanted.

 Lightforged draenei - "For untold millennia, the Army of the Light waged war against the Burning Legion throughout the Twisting Nether. The draenei most committed to their long crusade would undergo a ritual to become Lightforged, infusing their bodies with the very essence of the Holy Light. After finally achieving victory on Argus, the Lightforged Draenei have undertaken a new mission: protecting Azeroth from rising threats and helping the Alliance push back against Horde aggression."

Always post a buyout price on your auctions. Don't think that "They'll just bid it up anyway." Many players will not bid on an auction with no buyout price unless the item's bid price is heavily discounted to begin with. This can lead to bidding wars, but in many cases the item will sell for a fraction of what you could have gotten if you had posted a buyout price in the first place. You will have more sales at a higher price and get your money more quickly if you post a proper buyout price.
Taking Herbalism and Mining as your two professions can be a lucrative way to level with the very stable and high prices of herbs and ore thus far in BfA. While rested, each mining and herbalism node will award nearly 4,000 experience points which makes it so that four to five herbalism or mining nodes is equivalent to one quest. If you have the Sky Golem mount for herbalism, you can pick herbs without losing mount speed. There are also enchantments for gloves that will increase the speed at which you can process the herbalism and mining nodes. These can be made rather easily by an enchanter and should be relatively inexpensive on the auction house. These enchants will pay for themselves with the time saved while herbing and mining. Remember to continue completing mining and herbalism quests while leveling up to increase the yield of each node making your herbalism and mining leveling experience exponentially more lucrative.
Special note: At 110 it's almost certainly worthwhile to go and immediately get your Heart of Azeroth and first piece of Azerite gear from the BfA opening quest. It doesn't take long and provides pretty high power levels. I'd then return to Legion quests until 111 or even 112, since the power of these items will increase your kill speed significantly over the scaled enemies of BfA content.

The world quests aren’t necessarily bad, but they aren’t good either. I wouldn’t mind killing five of a type of monster or fighting one particular boss a few times, but after seven or eight, it starts to wear pretty thin. But going from levels in the mid-20s can take nearly 30,000 AP, so you’ll need more than world quests if you want to get your heart up in a reasonable time.

The most simple thing is TradeSkillMaster. This AddOn shows you quite an amount of information in the items tooltip. In my opinion, DBRegionMarketAvg the best source. It tells me the price, an item was posted on all EU realms in the last 14 days. Why not DBMarket? DBMarket only shows you the items value from your server in the last 14 days. This value often gets manipulated. Some people start to post an item with a 500g value for 500.000 Gold on the auction house for several weaks. As a consequence, DBMarket is rising towards 500.000 Gold.  If you use DBMarket with 100% and post your item for 500.000 Gold, nobody will buy it.