There are more passive methods to gain wow classic gold, but these are slower. For example, many people choose to fish in places like Tanaris, or kill Harpies in Feralas and loot items such as mageweaves. These are rather AFK-able, but again, not as rewarding. Some people choose to favour fun over anything, and like in any MMO (massively multiplayer online game), the best way to have fun is playing games with friends or your guild. Dungeon runs with your friends provide social interaction and are definitely helpful over the long-term for your gold stack!
When it comes to levelling the Priest Class from 1-60 fast, XP grinding locations is only half the battle. You will need to make sure your weapon does enough DPS so that you can clear these mobs fast enough, it should also be noted that monster should be around your level to make sure to gain the 100% XP Reward. The Level your character should be before you start that specific location will be indicated to left in a Blue Color for Alliance [Lvl 35-39] and the Orange Color for Horde [Lvl 35-39]. The Mobs you are looking for in that specific area names are Bolded [Mob Name].
I am currently working full time on my Vanilla WoW leveling guides. Soon there will be a 1-60 speed leveling guide for Alliance, along with in-game guide versions available for my members area. As of right now, there is no members area, but if you would like to show support for my efforts into this project, you can simply donate to me via Patreon if you like (you will get some cool rewards in return). Or you can donate directly with PayPal if you like. All donations are highly appreciated and they will only motivate me more to continue making the best vanilla WoW leveling guides on the web.