If you really want to optimize your collection, you should wait until the end of the event and choose the pack with the most unowned cards
Multiple instances of rebound on the same spell are redundant (that answers my question from the last section!)
Entropic Battlecruiser One charge counter is all thats preventing Entropic Battlecruiser from being a strictly better Megrim/Liliana's Caress
You could run a token deck, populate it with adorable anime squirrels, illusions, or spiritswhatever makes sense
After being countered, a spell card goes to the graveyard
There are a few aspects that hold it back from being more complex and competitive, namely a lack of card draw and ways to mount a comeback and counter the opponent, but those issues may be alleviated as the game evolves