shards/crystals/clusters

[mdha02]

Or they could come up with a way to break clusters into crystals and crystals into shards.

[ChameleonMS]

Shards are easy to get - just send out your retainer(s) to gather them while you are doing something else.

This unfortunately is one of the least efficient uses of your retainer. It has been awhile but IIRC you get 60 shards per venture.
Shards sell on the MB for approximately 30-100 gil. (I cannot speak to the economy of all servers of course). Thus, all you need to do is have your retainer get you anything that is worth about 6k per venture to equal the shards produced by a venture.
I can usually send my retainer to get me stuff worth 15K-30K, thus, with that same venture I am now able to purchase 150-300 shards.