How to make Gil?

[Arasiel]

What's a good way to make Gil? Mine? Craft? Farm?

[ASnogarD]

Initially just level up a character to 50, then a gatherer and / or crafter (some say level all the crafting jobs to 15 at least then select 1 to max out... to make HQ items)...gatherers sell high end materials for HQ items that crafters make to sell to players who spiritbind the items and turn them to high end materia (IV's, tho resistance materia is not as popular).
Basically you got to find a spot in that materia cycle chain, and earn gil through one or more of that chain...Mats -> Craft Item -> Spiritbind item to Materia. The high end Materia is in high demand, hard to acquire and therefore lucrative.

At least thats how I understand things... I may be mistaken as I am still leveling.
Hope it helps.

[ShadowDan]

Counterfeiting.

[Shirai]

If you are not looking to make a lot in a short time, any of the ways that you yourself named can give you a reliable income.

[Toranja]

Buy large stacks. Sell small for premium. Highest return/work ratio.

[Maero]

Or if you have no intention on doing any crafting you can sell your shards.
If you have lots of them you can make good gil. Check the market boards on what sells best. Also iron ingots sell for good gil as well, which is from mining

[CalvatE]

Mining has given me some profit. Usually I sat just on 900k by selling Philosophy materials.

To begin mining I lost about 100k, after buying the top tier gear and its required materia.

However after 2 days, for about 4 hours each day I've netted myself about 100k profit back.