@IlISupaIlI Honestly, I think the quickest way is being good and having a good partner. Can't stress that last point enough.

First question is what you need the fortunes for. If it's to buy scripts for multiple characters, I think Archive is just a really expensive way to get those, regardless of how good you are. I had 200K saved. The second week, I needed more. Yes you can solo farm one or two arcs relatively quickly, but the NPC only rewards you 550 extra and the bosses don't yield that much at low arcs. If you like brain-dead gameplay while listening to podcasts, maybe this isn't bad on multiple characters, but ... eh.

The reason I had 200K saved was that I'd played with a friend, who was heavily combat optimised. My own Arcanist is decent. I'm not a top parser, but I do ~92K on the trial dummy. My friend frequently did double the damage, even in the first arc. How? I'm still scratching my head. While Flail is still an execute, I think one of the keys to mob killing is probably to not use Fatecarver all the time, even at 3 crux. He might have been a templar, though. He would constantly swap gear with an addon. He'd use Dark Convergence for one add pull. He'd swap to a different set for the next, while Dark Convergence was on cooldown. He would use setups like Mechanical Acuity + Elf Bane for a long running destro ult and nuke down bosses like crazy.

Later on it becomes a question of luck with your visions. Once you have all the Archive buffs, Focused Efforts yields +500% per vision. It is the single most important one. If you don't get a few of those, don't go deep. If you do, make sure you have an Archive build to take advantage. This is really too big a topic for a single forum post, but Unleashed Terror guarantees AOE Hemorrhaging, whereas a Warden can cause AOE Burning with the Ice Furnce set.

You want to do the side quests, especially the shorter ones, since they're the same fortunes as a boss kill. It's best to do it as a duo. The higher you go, the more fortunes per boss you get. Yes it gets harder and slower, but that's where being a top DD and/or having one as a partner comes in. That said, one player being an outright tank from the beginning can work, since pulling mobs together helps the DD quite a lot. If you want to go far, bring a tank, but even prepare your DD to become tanky via gear swap. In the later arcs, it's the visions that carry your damage. Oh, and don't forget to kill those scamps in the boss fights, or whatever they are.