This option is better to use at level 40+. Higher level you are is better, more money you make then. All you do is farming dungeons or specific bosses. Here you kill a few birds with one stone: you get lots of experience (make sure you have all quests in your quest log, always ask your teammates to share) if you are still leveling; improve your current gear; and loads of loot (clothes, recipes, even crappy grey items selling for a lot to a vendor). If you are in a group, think about your groupmates if they need an item or not, don’t roll need on everything.
To get back to Classic for a bit, this is what I think is happening. Players who prefer the old ways (and full disclosure, I'd count myself among them, but to a smaller degree than most) complain/talk about the negative sides of modern WoW and Battle for Azeroth in general. While they do this they also talk about how things were better before and often mention Vanilla as a reference point. People who enjoy BfA now feel attacked by this and so they retaliate. Hence, liking Classic means you either have nostalgia goggles on or have no idea what you're talking about and will hate the same things you say you want 2 weeks after you start playing it. It's an amazing thing, where literally each side is doing to the other what they feel is being (wrongly) done to them. I feel like writing this is the most redundant thing I've ever done, and yet I also feel that it needs to be said, because it seems some people just don't get what they're doing, or at least I hope they don't (some do and are doing it on purpose but there's trolls everywhere so there's no point in even discussing them).
Warrior should be a go-to choice for everyone who wants to get into the end game. Protection Warriors in Classic WoW were considered as one of the best tanks, Fury talent build was a great option for DPS while Arms were dominating PvP environment. However, Warriors’ strength relies on the character’s gear, which means that you might need to put some hours into finding the right items for your class. It is also worth mentioning, that Warrior might be one of the hardest classes to level up in World of Warcraft: Classic but rest assured, if you’ll manage to hit the level cap and find suitable gear, Warrior is one of the strongest classes in the game.