The marketplace for the Pokmon TCG is turbulent, but generally speaking, three traits tend to guarantee a card having value: being nostalgic (e.g., being an Eeveelution), being a Legendary, and/or being a Secret Rare or Alt Art
Otherwise, put Approach of the Second Sun into its owner's library seventh from the top and you gain 7 life
Pairing this with an aggressive red deck, an unblockable blue threat, or even a low-to-the-ground green behemoth will knock opponents out of the game before they can blink
With a reasonable retreat cost and HP count, there are plenty of reasons to play M Gengar EX
Your Journey's End partner will review and discuss your collection
The other Final Fantasy Commander decks also look pretty cool, and each have a big bold approach (you can check out all the decklists here), but I'm really drawn to this aggressive approach