Biggest gainers over the last 30 days, by TCGplayer median. Historical movement — not investment advice.
64 cards moving ≥ 10%.

Regidrago V
Silver Tempest

Greninja ex
Twilight Masquerade

Bea
Vivid Voltage

Mimikyu V
Battle Styles

Vaporeon V
Evolving Skies

Lady
Lost Origin

Rayquaza V
Evolving Skies

Zeraora V
Chilling Reign

Roxanne
Astral Radiance

Umbreon V
Evolving Skies

Garchomp ex
Paradox Rift

Plumeria
Burning Shadows

Ampharos V
Vivid Voltage

Suicune V
Evolving Skies

Slowking ex
Paldea Evolved

Crispin
Stellar Crown

Galarian Zapdos V
Chilling Reign

Lapras ex
Stellar Crown

Rayquaza V
Evolving Skies

Ninetales V
Rebel Clash

Sylveon-GX
Guardians Rising

Espeon-GX
Sun & Moon

Galarian Slowking V
Chilling Reign

Alolan Ninetales-GX
Guardians Rising

Gardevoir ex
Paldean Fates

Tornadus V
Chilling Reign

Sableye V
Sword & Shield

Galarian Articuno V
Chilling Reign

Buzzwole-GX
Crimson Invasion

Galarian Zapdos V
Chilling Reign

Gyarados ex
Scarlet & Violet

Olivia
Crimson Invasion

Zacian V
Sword & Shield

Colress's Tenacity
Shrouded Fable

Milotic V
Rebel Clash

Houndoom V
Darkness Ablaze

Tapu Koko-GX
Guardians Rising

Dragapult V
Rebel Clash

Galarian Articuno V
Chilling Reign

Mew V
Fusion Strike

Silvally-GX
Crimson Invasion

Galarian Moltres V
Chilling Reign

Umbreon-GX
Sun & Moon

Dragonite V
Evolving Skies

Doctor
Chilling Reign

Flareon V
Evolving Skies

Hisuian Sneasler V
Astral Radiance

Pokémon Fan Club
Ultra Prism

Glaceon V
Evolving Skies

Darkness Energy
Crown Zenith

Darkrai-GX
Burning Shadows
Boss's Orders
Ascended Heroes

Leon
Vivid Voltage

Mega Gardevoir ex
Mega Evolution
Mega Zygarde ex
Perfect Order
Meowth ex
Perfect Order

Giovanni's Charisma
151

Xerosic's Machinations
Shrouded Fable
Forest of Vitality
Perfect Order

Dawn
Phantasmal Flames

Lana's Aid
Twilight Masquerade

Teal Mask Ogerpon ex
Twilight Masquerade

Luxray V
Astral Radiance
Beedrill ex
Chaos Rising