What are the best ways to make gil?

[Krotoan]

I have heard that treasure hunts are one of the best ways to make gil. What other ways are there? It seems like the game rewards you quite a lot of gil just for playing, but not quite enough to amass enough gil to be in the millions that I heard people are at!

Treasure maps and the hidden dungeons they award (you will need a party to do the hidden dungeons though)
Run your duty finders daily and roll on everything. Desynth everything you get (you will need to have every crafting discipline to do this though). Sell the results.
Keep your retainers doing quick ventures and sell the results (or again desynth and sell the results) some of the stuff they bring back is worth hundreds of thousands.
Work the market board: Find things that NPCs sell but people for whatever reason buy for higher prices on the marketboard like the unglamour prisms and lots of the low level crafting mats. You can make pretty consistent and decent profits like this.