There are some people who happen to have considerable gil from exploits, but let's disregard that because it doesn't help or apply the majority of us.
Crafting has potential, but I think it strongly coincides with 1) luck and 2) the demand for the pieces. A Goldsmith friend of mine noticed that he didn't have many good options since there's a glut of Souveran -1 floating around our server (goldsmithing, despite the costs, seems to be very popular). If you luck out with a HQ, you're still stuck with finding a buyer, not to mention dealing with all your NQs.
Anyway, a brief list of stuff that still has some good value (at least on ol' Sylph):
- Vagary stuff, Dark Matter especially right now
- Delve items, notably Cehuetzi Pelts and Waktza Crests
- Voidwalker mats, notably Ethereal Squama and Befouled Silver
- Voidwatch stuff, notably HMPs, cinders, Sealord Skins (mats for relic 119 crashed hard due to a recent login campaign)
- Some Legion materials like Ormolu ingots and Staghorn Corals
- Unity materials, notably Escha pops
- Alluvion Skirmish stones (surprisingly, skirmish is still a thing)
- Eschalixirs, with a guaranteed +2 for each Azi Dahaka/Naga Raja if you max your evaluation
- ye olde currencies
...and I just realized I more or less repeated everything ikariiiii said. Oh well.