Like most Pokmon cards, the value of Gyarados 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 (XY Black Star Promos)
Tortured Existence is a one-cost enchantment (so it stays on the board once played), then you can pay one mana and discard a chosen creature card to return a creature from your graveyard to your hand
Furthermore, discarding a specific card like Echo of Eons, Wonder, or a shuffle Eldrazi such as Kozilek, Butcher of Truth has some nice synergy
If you arent interested in competitive Magic and just want to play for fun regardless of budget, Commander is perfect theres a reason its the most popular paper format
Despite being better than Captain Hook, Mickey has a high in-game cost of 8 Ink