The shop is where you can spend gems on booster packs or spend real money on gems.
7 booster packs are available:
Every day, one unit will be sold directly from the store. Prices vary by rarity. A Commons will cost 20 gems. An Uncommon will cost 90 gems. A Rare will cost 250 gems. An Ultra Rare will cost 1200 gems. Legendary units will not be sold individually.
Commander Booster Packs cost 400 gems each. They contain 10 units: 4 Commons, 3 Uncommons, 2 Rares, and either an Ultra Rare or a Legendary. Only units released since v1.40 and before v2 are available.
The Starter Bundle costs 2000 gems. It contains 60 units: 44 split between Commons and Uncommons, 11 Rares, 4 Ultra Rares, and 1 Legendary. Unlike the other booster packs, the Starter Bundle can only be purchased once.
Gems can be purchased for the following prices:
450 gems: $5
1100 gems: $10
2300 gems: $20
5600 gems: $50
This is not the only way to get gems. Gems can be earned through Quests.