Gems

Description
Shards are an item dropped when defeating any kind of Pokémon. These typed shard can be invested into the Shards tab to increase type effectivity, and your damage output.

Upgrades
To max out an entire tree is 110,000 of the respective shard type.

Helpful tips
The shard types reflect whatever type(s) the Pokemon defeated were. Defeating Pokemon in a Dungeon give you 3 Shards of whatever types the Pokemon was, however defeating the boss will give you 20 Shards. Pokemon in Gyms give you 5 shards each, and Wild Pokemon on Routes give you 1.

Effectivity Chart
Type and shard effectiveness