While leveling, try to make use of the new Battle of Azeroth experience gem, Insightful Rubellite, which gives you +5% experience. Equipping one of these requires a socket in your gear, so try to hold on to a piece of Legion gear with a socket or acquire one of the Legion Legendary rings since every class has one. Each of the rings includes a socket. You can acquire one of these rings rather easily by doing World Quests in Legion zones and acquiring 1,000 Wakening Essences that can be used to purchase a legendary ring in the Legion version of Dalaran.
Much like an encounter with a wild pet team, PVP Pet Battles are turn-based. However, unlike the PVE version, the PVP combat system is timed and any ability for each round must be chosen within that time limit otherwise it will assume you have passed a turn. A time penalty is applied if you take more than 15 seconds to choose an action, resulting in progressively shorter round timers for you.
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.
SSC has been known for it's abundance of pet drops, which is why this farming spot exists. It can only be done once a week by each of your characters, so make sure to hit it if you can. Generally you'll want to kill all the bosses for a chance at their rare pets. Everytime I go, I have the luck of getting one, in the video I actially got the Tideskipper to drop, and a video I done on the spot before that, I got the tainted waveling. So yeah. It's a pretty awesome spot with high rewards and also some world drops. I was able to snag a will of edward the odd as well, totalling a nasty 35,000g. The most important part is that you kill the bosses, the pet drops do sell, and they are very easy to get. Well worth the time invested.
If you already have a high level character or a friend willing to give you gold then you can purchase Heirloom items. These items are bound to account and are accessible through the Heirlooms tab using Shift+P. The benefits of these Heirloom items is that they scale with your level keeping your gear up to date without you having to worry about upgrades, and they provide a significant XP bonus.
If i start on a new realms, I am farming a lot of transmog from classic and Burning Crusade Dungeons and Raids. In the beginning, i start to post them if they have at least a DBRegionMarketAvg (Average value of an item on all EU realms of the last 14 days) of 500 Gold. All the other items get vendored. The time you hit a stock of 1000 Items, my value treshold raises to around 2.500 Gold. All the items below that value get vendored aswell. Newly farmed items that are above these treshold will be listed. Why? If I start over somewhere, I want to get a certain amount of gold quickly. Cheap items are great for that. Later on, to save time, Quality is better than quantity. As mentioned above, re-posting the items on the auction house takes quite a bit of time. At this point, I can recommend you the TradeSkillMaster AddOn, it makes your auction house work really a hell of a lot easier.