I've had to do it myself, especially on an alt with hardly any gil or that just beat the MSQ.
If you scrape and claw you can get there pretty fast. Get your 560 job artifact gear, do your weekly hunt bill and daily level 3 hunt bill for Shadowbringers and Endwalker to get 350 Sacks of Nuts and buy 590 gear with it, do daily roulettes for gil and tomestones, sell any valuable loot on the market board or to a vendor such as materia and sell any useless loot for GC seals or gil as well. Buy the most valuable thing you can with poetics and vendor it for some gil. Sell your GC seals for the items that vendor for 360 gil.
After that, you can buy some left-side uncapped tomestone gear and world visit to find the cheapest priced crafted gear even if you only have enough for 1 piece of gear. Start clearing the normal raids and get the right-side drops and exchange for them. Do the same for each tier and gradually boost your right side item level significantly.
Continue with the MSQ and unlock all the dungeons, equipping any left-side loot that drops and is an upgrade. Finally, unlock Expert roulette and do that. Then purchase your weekly-cap tomestone gear piece.
And by now, your item level is pretty decent. It can be improved further by doing the alliance raids and getting all the drops from there.
Not all of that is necessary and just doing some of it will work, but the point is you don't necessarily have to buy crafted gear to get high enough to progress MSQ, it is just the quickest and easiest way to explain to a new or returning player if they have the gil.
Farming leveling dungeons would not really be useful at any point in my opinion, since the MSQ always drops the gear you need for the next leveling dungeon as a coffer and at max level you have the job artifact gear. So the player was misguided in doing this.