One more thing to keep in mind right now is that the market is kind of hurting at the moment. Lots of relevant things are not so much in demand right now like they were in the first month of expansion, and MIGHT be again in the first week of patch (though possibly with different items), and lots of people are overdoing the supply because they wish to wrap up fundraising for the big house hunt that's coming (and going) in about 72-73 hours from the time of writing this post.

Making money might be rough at the moment, but keep plugging away. Just talking low level mats--I don't know your gatherers' levels at the moment--sell gathering mats that remain relevant, such as silver ore, effervescent water, cobalt ore, and uhh... I sadly forget if anything from Botany (though, to be fair, it sometimes seems like the devs do too). Try getting materia to sell through spiritbonding your gear. Do your daily hunts and roulettes, as well as weekly challenge log entries, for the easy gil they all provide. Also, be ready to save tomestones and GC Seals for materials, just in case. I'm not so sure you'll make the amount you're asking for in a week, but you'll at least be making something.

On patch day, especially during the early hours, keep an eye out for what mats will suddenly be in high demand. Those will spike. It's not sustained, but it's something too.

Hopefully, the market won't be swamped by other people all thinking the same thing. It'll be like traffic hour on the freeway, and that might get aggravating.