whatever it is that makes cards cost more or less money, after accounting for "card rarity")
Charizard EX, for example, can hit for 200 damage with Crimson Storm but that attack costs four Energy to use: with a lucky Moltres turn, though, Charizard can instantly have three Energy before it even evolves
Emerald Dragon is a great example of how to give card advantage without drawing cards, though Id argue that white deserves it more and has the more playable version in Crystal Dragon
If an effect would set your life total to a certain number that's different than your current life total, that part of the effect won't do anything
"One Piece TCG: Cardboard Card Storage Box - Zoro & Sanji" falls under the category of Game Supplies.
You can still run other themes in your deck, but having a couple of Mutate 3/4 CMC cards in your deck gives you the ability to build your own bomb to either win the game or put out a creature to stop your opponent