First Aid is a relatively easy profession that is very possible to level to 300 while you are leveling your character from 1-60.
Secondary, but still useful! Guides for the classic secondary professions are available here.
Many players don’t know that Fishing can be an excellent way to make money in Vanilla World of Warcraft. In fact, fishing might be the best way to make money at low levels. You can start making crazy amounts of gold as low as level 20. Here are a few ways that fishing can make you a ton of gold in WoW Classic: