Like most Magic: The Gathering cards, the value of Fishing Gear 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 Commander)
The uncounterable part actually matters in limited, because it means this can hit Disguise creatures and you dont have to worry about Ward
A combination of low-cost Characters and reanimation abilities allows the Amber and Amethyst starter deck to flood the board state with threats that can rack up Lore quickly while Challenging an opponents Exerted Characters
Mogis, God of Slaughter Mogis, God of Slaughter enables tons of chaos strategies thanks to its color identity
Ten were Ruby/Sapphire, five Sapphire/Steel, and just one Amethyst/Sapphire
As long as you can consistently hit a decent-sized creature and make sure that the combat trick aspect of the card gets value, its hard for Yunas Whistle to be anything worse than good