In Japan, the bulk of the sets cards come from High Class Pack: Shiny Treasure ex , which was released on December 1, 2023, while the English release was on January 26, 2024
While being inexpensive is a huge factor, its not the only thing to look for
You'd probably guess this, but to avoid any confusion, the Mewtwo EX is found in the Mewtwo pack, the Pikachu EX in the Pikachu pack and the Charizard EX in the Charizard pack

Sort Rarity Card Type Bulbasaur #1Common $0.25 Ivysaur #2Uncommon $0.18 Venusaur #3Holo Rare $0.92 Radiant Venusaur #4Radiant Rare $9.18 Alolan Exeggutor V #5Ultra Rare $0.81 Spinarak (Peelable Ditto) #6Common $13.98 Spinarak #6Common $0.21 Ariados #7Uncommon $0.13 Charmander #8Common $0.26 Charmeleon #9Uncommon $0.20 Charizard #10Holo Rare $3.27 Radiant Charizard #11Radiant Rare $18.85 Moltres #12Holo Rare $0.43 Numel (Peelable Ditto) #13Common $13.57 Numel #13Common $0.17 Camerupt #14Uncommon $0.11 Squirtle #15Common $0.30 Wartortle #16Uncommon $0.22 Blastoise #17Holo Rare $2.00 Radiant Blastoise #18Radiant Rare $11.15 Slowpoke #19Common $0.20 Slowbro #20Uncommon $0.18 Magikarp #21Common $0.15 Gyarados #22Holo Rare $0.37 Lapras #23Holo Rare $0.28 Articuno #24Holo Rare $0.39 Wimpod #25Common $0.11 Golisopod #26Holo Rare $0.26 Pikachu (27) #27Common $0.34 Pikachu (28) #28Holo Rare $1.63 Zapdos #29Holo Rare $0.42 Mewtwo V #30Ultra Rare $5.75 Mewtwo VSTAR #31Ultra Rare $7.72 Natu #32Common $0.08 Xatu #33Uncommon $0.11 Lunatone #34Uncommon $0.13 Sylveon #35Holo Rare $0.82 Onix #36Common $0.12 Larvitar #37Common $0.12 Pupitar #38Uncommon $0.15 Solrock #39Uncommon $0.10 Conkeldurr V #40Ultra Rare $0.61 Alolan Rattata #41Common $0.13 Alolan Raticate #42Common $0.16 Tyranitar #43Holo Rare $0.28 Steelix #44Uncommon $0.12 Meltan #45Common $0.12 Melmetal #46Holo Rare $0.17 Melmetal V #47Ultra Rare $0.71 Melmetal VMAX #48Ultra Rare $1.53 Dragonite V #49Ultra Rare $4.13 Dragonite VSTAR #50Ultra Rare $4.19 Chansey #51Uncommon $0.16 Blissey #52Holo Rare $0.27 Ditto #53Holo Rare $5.59 Eevee #54Common $0.26 Snorlax #55Holo Rare $1.42 Aipom #56Common $0.16 Ambipom #57Common $0.17 Slaking V #58Ultra Rare $0.71 Mewtwo V (Alternate Full Art) #72Ultra Rare $64.84 Mewtwo VSTAR (79) (Secret) #79Secret Rare $52.13 Dragonite VSTAR (Secret) #81Secret Rare $48.07 Mewtwo VSTAR (86) (Secret) #86Secret Rare $36.30 Radiant Charizard #11Radiant Rare $18.85 Dragonite V (Full Art) #76Ultra Rare $18.26 Bidoof (Peelable Ditto) #59Common $17.84 Spinarak (Peelable Ditto) #6Common $13.98 Numel (Peelable Ditto) #13Common $13.57 Melmetal VMAX (Secret) #80Secret Rare $11.51

Ungraded & graded values for all Pokemon TCG Gym Challenge Pokemon Cards