Although WoW currency can be found through quests, fallen enemies or the dreaded "farming" process, doing it the conventional way is time-consuming. Considering the upcoming release of the Legion expansion pack in August of 2016, stocking up on gold is more important than ever. This way, you can spend less time farming and more time buying everything you need to tackle the next set of challenges.
Loot everything - Every single item in the game has some value and you should take advantage of this fact. Grey items can be vendored for that little bit of extra pocket money and white stackable items are needed for crafting, which means that people will generally buy them if you post them on AH for low enough price (if you can't be bothered to post Auctions, you can just vendor all of them and be done with it). Some of the looted items will rise in value over time, so you might also want to take your time and store them on Bank Alt.
I really can't buy into this reason because they used to do beta without the subscription requirement. It seems like if they want to test how many people are interested, they can just open it up to everyone like they do for every WoW expansion. And how are they going to know how many servers they need for all the people without a subscription who can't reserve a name or qualify for beta?
Some players have been surprised by these apparent flaws—even players who have been eagerly awaiting WoW Classic's release based on fond memories of vanilla WoW. In truth, it has been so long since WoW first released, players' memories may not always be accurate. Some details might be fresh, but others might be lost in time, and it's those lost details that could surprise players revisiting the original experience in WoW Classic.