DM North is by far the best way to go, you can very easily do a run in 15 minutes or less with a day or so of practice.
You do need to be either engineer or blacksmith, and you don't need invis pots, but one potion speeds the run up by 1-2 minutes, so it's definitely worth it for how cheap they are.
Though by now most people have the items they want out of tribute, it's much harder to find a buyer for rings and lodestones, so its profitability has definitely dropped. I still run because it's fun and reasonably challenging, good way to pass the time. Definitely get a good sense of accomplishment figuring it out the first time.
I'm not going to ruin the surprise, but you can very easily pull Gordok alone, if you've ever split a pull as a hunter you should know how to do this
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