TwistedPretzel

What to upgrade next

1. 
   ZapLevel 14 → 15In 3 of your 10 best decks · 0.7 levels below those decks' average
2. 
   FurnaceLevel 14 → 15In 3 of your 10 best decks · 0.7 levels below those decks' average
3. 
   Ice WizardLevel 14 → 15In 2 of your 10 best decks · 1.0 levels below those decks' average
4. 
   Electro WizardLevel 15 → 16In 4 of your 10 best decks
5. 
   FireballLevel 15 → 16In 4 of your 10 best decks

Based on the 10 best popular decks you can already play. The API doesn't include gold costs, so this ranks by how much an upgrade helps those decks, not by price.