Who needs money? Crafters, who needs shards?
This could be about crafting, or it could be about markets, but it's really about making some gil fast.
This is something that will work once per character. It's very lucrative and simple for non-crafters to do. For crafters on alts, it's a great way to save money.
When you join a crafting guild, you are given two back-to-back quests that involve (1) talking to a receptionist, (2) talking to the guild leader, (3) equipping a tool, then (4) talking to the guild leader again. Doing so gets you 250 elemental shards of one type and 150 of a different type.
In the time it takes you to travel between the 8 guilds, right click through conversations and equip a tool, you can make over 165,000 gil. Sound interesting? Keep reading.