Many cubers take a lot of pride in building their cube using specific versions of the cards, foils, or alternatives, but you can totally just buy the cards the cheapest version of each card if you prefer
The card lists Mewtwo at 70 HP with Barrier as a zero-cost move that reduces incoming damage, a mechanical nod to the psychic shielding ability that defines the character's combat style
Training Grounds can reduce the part of an activation cost represented by generic mana symbols down to nothing, as long as it still costs at least one mana
For the Common Good Worst case scenario, For the Common Good is a card you use to recover after an opponent has decimated your life total
I played Diamond on the DS, and Piplup was my starter
Since you can fetch lands and search up lands at instant speed, you can do this on your opponents turns to set yourself up for a strong attack on your next turn