The four decks are built around four iconic entries from the mainline Final Fantasy series: Revival Trance, based on Final Fantasy VI
That can really shift the tide of the game by either keeping some of your characters safe from challenges or keeping certain abilities from being put into play.
The Emperor, Hell Tyrant (Yawgmoth, Thran Physician), Hero of Light (Adeline, Resplendent Cathar), Terra Branford (Urza, Lord High Artificer) and Astral Titan (Primeval Titan) and Seymour Gado (Kinnan, Bonder Prodigy) are the strongest cards within their archetypes
They spend a good chunk of the game catching frogs in Qu's Marsh (there's even a golden frog sidequest), while their main battle ability is actually "Eat" - consuming weakened enemies to learn Blue Magic (enemy skills)
You just need to lock the game down until your opponent is out of cards in their hand, and then slowly chip away at them
Lastly, if the card says draw on it, its a good card