Efficiency can be determined simply by the reward you receive at certain mana costs (Counterspell and Cancel do the same thing, but Counterspell costs less), the total payoff you receive from a single card (Hull Breach and Decimate are both good cards, but Decimate usually covers much more ground), or the payoff you receive in conjunction with other cards (Anointed Procession makes other token production cards completely absurd if unchecked, which is usually better than adding one more card that simply makes tokens like Spectral Procession in a token strategy)
With all of that said, I am sticking with Olivia as our commander here
Several cards in the set refer to modified creatures and reward you for making your presumably already awesome creatures awesomer
Seedglaive Mentor gets a little permanent pump and is complemented nicely with the cantrip red instant, Might of the Meek
Spit Flame
The artwork is dynamic and colorful, featuring the Sky High Pokemon in all its Mega-evolved glory, with the elongated serpentine body coiling across the card in a composition that emphasizes the sheer scale and power of one of the most popular Legendary Pokemon ever created
