Gems

Description
Shards are an item dropped when defeating any kind of Pokémon once the player has the Shard Case unlocked. These typed shards can be invested into the Shards tab to increase type effectivity, and your damage output.

Upgrades
To max out an entire row costs 27,500 shards of the respective type.

Helpful tips
The shards you get from defeating a Pokémon depend on the type(s) that Pokémon has. Wild Pokémon on routes give 1 shard per type, dungeon encounters give 3, gym/trainer Pokémon give 5, and dungeon bosses give 20.

Optimal gyms (efficiency)
Most of the below gyms or trainers give 5 shards of the relevant type per Pokémon fought (i.e. every Pokémon in the gym has that type).

Type effectiveness chart
Type and shard effectiveness