Like most Magic: The Gathering cards, the value of The Fire Crystal depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
CARD WITH THE CENTER IMAGE AS
Then I tossed in Circle of Dreams Druid to do the same
Of course, the cards are no good if you can't use them to take part in casual battles too
Venusaur EX Illustration Rare (198/165) No points if you guessed this one
It will also be focused on designing cards that could likely be printed on cards by Wizards of the Coast, and most likely in a standard set (planeswalker deck planeswalkers are balanced completely differently, and supplementary set ones are also separate from that) but card creation is still a creative act and, in the end, youre the only judge of what you can or cannot do on a card