Energy, a new type of counter used as a persistent, special currency that can be both created and redeemed by plenty of cards in Kaladesh
Because I'm lazy
Even Red ended up contributing more to this deck than I expected, not just with some good creatures but also Relentless Assault to double our combat damage output, Fervor to give our stuff haste, and both Price of Progress and Pandemonium which gives the deck some reach with burn to finish off low opponents
Pricier options include Sword of Fire and Ice, Memory Jar, and Wheel of Fortune
By default, when you use Richard's ability, you are limited to cards legal in the format you're playing
Some packages will be universal, while others will be deck specific