Don't put all your eggs in one basket. It's a lot better to spend your working capital on buying forty items for auction, each with the potential for profit, than to take all your working capital and invest it in that one purple leatherworking recipe that you hope will make you several hundred gold. If that puppy doesn't sell, or doesn't sell for what you want, you've just wasted all your working money, and deprived yourself of a lot of flexibility. Leave speculating on purple items until you have a few thousand gold squirreled away.
Each of those modes existed long before this latest expansion; raiding is a basic concept in MMOs, and Mythic+ was added in World of Warcraft’s last expansion. The problems with Battle for Azeroth’s endgame come from the systems it adds, which most often artificially gate progress where most of the fun can be found. If raids and Mythic+ are the carrot, we’re about to talk about the stick.
There's a good chance you can buy the raw materials for 25% - 75% of the going rate of the finished item, or mine them for free. The fee for an 8 hour auction is only 1 silver, so you can afford to re-auction rods that don't sell the first time. Be careful of making too many rods or other parts of a kind at once, though, as you may get stuck with them for a long time when others produce the same item and set a cheaper price to it.
The NPC scan and NPC alert method is an awesome way to build a stock of rare BOE items simply because you don't really have to try. By installing NPC scan and NPC alerts, you can literally just fly over anywhere and be alerted when you pass a rare spawn. As we all know, rare spawn loot tends to have higher item vales, as not everyone is able to consistently farm them. Some NPC's, especially those in outlands have those higher item values when compared to the rest of the world. As a goldmaking method I just everyone should be doing this. It only requires you download two addons and you can get access to important NPC,s that you would otherwise never knew existed. The opportunities are endless, I would generally never play without these cool addons. Realy cool.