You have a few nodes that boosts your gathering quantity by 1 if your elemental resistance is above a certain threshold. Use those elemental skills in your gathering class to boost your your gathering to 4 units. Pop a few cordials. Bam, you just gathered a ton of shards. If you're a hardcore crafter, then perhaps you should ask your FC to help you gather shards and crystals. You also have levequests tradecrafts that give shards too.

As for breaking down clusters into shards and whatnot, the devs basically said no due to balancing and programming problems.