Level 59 having trouble making gil.

[Maeka]

Consider getting a DoH up to 50 for Moogles.

Depending on your server, Glass Fiber can sell for a decent bit of money, though now that HW is old content, the price fluctuates. Not sure what all it is used in, but on Lamia the prices go from 8k all the way up to 30k per. Once you max your reputation with the Moogles, you can get 9 Kupo Nuts per day and it only takes 7 to buy one.

I imagine as time goes on, fewer and fewer people will mess with Moogle quests unless they actually need <Lv60 XP on DoH classes, so that will pull the supply down a bit, until they are in demand, then some people will go out and get them when the prices are good, etc. These Moogle Quests are also nice for quick crystals; 3 quests that yield 20 Crystals each of various elements. If you don't plan on doing any serious crafting, you can sell the crystals on the market.

That also leads me to another point: Getting a DoL up to gather Crystals. Crystals (not shards) will always be in demand due to nearly every recipe in HW+ needing a minimum of 5 of various kinds for each synth. Some of the harder-to-get crystals tend to be Lightning and Wind, or at least from my experiences that's how it tends to be. I have 2,200 of each Crystal except for Lightning and Wind, I only have 1500 of those two, because the Moogles give them a lot more rarely than they do the others (especially Earth and Water, I've got a metric ton of those).

Leveling a DoL is easy, just use GC turn-ins every day, and each week make sure you do your Challenge Logs. You don't really need Scrip Gear, just get to 60+ so you can access all of the HW Nodes. Once you're Lv60, all crystals will have 100% Harvest rate, though you might want to try and push stats with gear to take advantage of Gather+ nodes; vendor gear should be good enough, esp the 61-63 stuff.

[Niwashi]

Consider getting a DoH up to 50 for Moogles.

Depending on your server, Glass Fiber can sell for a decent bit of money, though now that HW is old content, the price fluctuates. Not sure what all it is used in, but on Lamia the prices go from 8k all the way up to 30k per. Once you max your reputation with the Moogles, you can get 9 Kupo Nuts per day and it only takes 7 to buy one.

And while you're working your way up to the level for that, there are plenty of things you can make to bring in some fairly decent gil along the way, starting even at pretty low levels. For instance, I've been getting 8k pretty reliably for HQ Aldgoat Leather, and that's a level 17 recipe (though you might need to be a bit above that to reliably HQ it). Of course, it wouldn't maintain that price if too many people try the same one, but as you go up higher in levels you get access to more items to make/sell, so it gets easier to find one that not many others on your server are providing. For that, you want to look for crafted materials (ingots, leather, cloth, lumber, ...) used in multiple recipes, and find one or more that your market isn't currently over-saturated with.

[Maeka]

Or, indeed, Crystal Shards might even still be going for decent prices, because I would imagine that many people are now farming Crystals instead of Shards, though the demand might not be as high as it was pre-HW. And indeed low level materials, especially those gathered could bring in some money.

I imagine Velveteen is still expensive; you can probably quest Sylphs and buy Velveteen Threads and resell them on the AH for far more than you bought them for, but again, do your research to see if this is feasible first.

Basically just run down through the list of materials and see what sells. I remember awhile back when I was in the low 50s, I managed to sell some Rosewood for like 500-800 per log. That crap adds up fast.

[Kaurhz]

Although many people do recommend levelling up DoL/H jobs, there's plenty of other very good opportunities to make gil, albeit not as fast or reliably, but it's an investment.

I do believe you can use poetics for the old Heavensward materials such as Eikon Mythrite. This extends to when you get Level 70, when you don't use your verity you can get valuable materials.

Also, bear in mind if you have been levelling up your GC ranks you can also get materials from the later ranks, such as the Arachne Web, I'm not entirely certain how well these materials sell now, bearing in mind a new expansion was just rolled out and a tonne of people traded gear for GC.

I would also advise getting and actively levelling up your battlecraft retainer if you have one, set it to the same class as your main and just send it out on ventures, they're fantastic for something that can be done so passively and as a 0 expense.

If you like taking a little bit of risk and don't mind the investment, you can attempt to flip items on the market, so where you buy items from a vendor, then resell them on the market at an increased price. There's a whole tonne of items that can be resold at a significantly higher value, such as most battlecraft and DoH/L gear, not to mention items such as Potter's Clay

As regarding your DoL classes you can level them up slightly as there's a whole plethora of low level materials that are valuable and used in high level crafts, such as Flax, and Effervescent Water, Flax being used in Varnish which is a base material for current crafts, and Effervescent, which is used for Twinthread