A 4/3/1 Evasive for 4 is not good
Sworn to Darkness Ob Nixilis of the Black Oath really represented a great moment in Magic story, in that his associated short story got redesigned to give backstory on the popular character and set up for his eventual re-sparking only a year later
Elemental Bond is probably the one Id get first, because it can trigger off of tokens, has no restrictions to how often it can trigger, and gates the trigger at three rather than four
Panharmonicon Combo While a lot of early Panharmonicon builds mostly focused on using the artifact for value, eventually, we realized it was possible to use Panharmonicon as a combo piece
Special Card Treatments Foundations features a bunch of different foil and showcase treatments that can impact the value and desirability of a card
Another thing to think about is not really color balance, but rather fairness balance