These books cost 1.000 Gold each and are sold from your BfA gathering profession trainer. As soon as you re-learned your farming profession, use this book and you will get back all of your lost Battle for Azeroth gathering ranks. Your gathering skill remains reset at 1, but you don’t have to care about that since you have your ranks back – thats literally all that matters.
This farm almost did not make this list. Even though I have had only a little luck with it, it seems to be gathering some popularity in the gold farming community. Although I feel with the recent changes in 7.3, this farm is very close to dying out. Generally what you want to to do is pull every mob you can as you venture to the last boss in the instance. The only saving grace of this farm (if you can call it that) is that some mobs are GUARANTEED to drop greens. Guaranteed. Whether or not they drop profitable greens is a different question, however it's a must-mention quirk you get from running this instance. It also allows you to get your hands on some rare low level blues.
Guild Banners. The Banner of Cooperation and Battle Standard of Coordination will increase the experience from kills. They both have a 10 minute cooldown, but when you use one, the other is only locked out for 2 minutes. I was very bad about using these, so it might be worth using a macro to drop them on your first attack against an enemy. Keep in mind you must have reputation with your guild before being able to buy these, so new character may have a bit of a wait before picking them up.
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.