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!
In terms of what the World of Warcraft Classic Best Classes are, Warrior and Priest stand out almost instantly. This is partly due to the fact that Protection Warrior is the only viable Tank Class in WoW Vanilla Patch 1.12. Both the Proc Warrior and Priest are required for Raids and when combined in a PVP setting can be a fierce combo on the battlegrounds.
You will have to talk with flight masters in most towns or cities you visit in order to gain access to that settlement's flight path. Flight masters who have a stop you have not yet unlocked will have a green displayed above their head (and on the mini map), much like a NPC with a quest. Unlocking flight paths as you progress through various zones will allow you to pay for a quick ride to a destination you have previously visited. This method of travel is significantly faster than walking or riding a mount.
A demo of the game was available at BlizzCon 2018, and was downloadable on home computers for anyone who purchased a BlizzCon ticket or virtual ticket. The servers became available when Opening Ceremony started at BlizzCon 2018 and was set to end on November 8, but was extended until November 12. Players started at level 15, and the only available zones were Westfall and the Barrens. It was based on patch 1.13.0, essentially patch 1.12.0 ported to a modern infrastructure. The first day of the demo, there was a playtime limit of a cumulative 60 minutes with a cooldown of 90 minutes, applied through the BlizzCon Exhaustion debuff. The debuff was removed on the second day of BlizzCon 2018.