I'd recommend the Charizard pack for your first few pulls, then alternating between the Pikachu and Mewtwo packs
So Aang refills your entire hand, reduces the cost of everything by WUBRG, adds immense pressure to the board, and, at worst, likely draws a card every turn
Anointed Procession, Mondrak, Glory Dominus, Doubling Season, and Parallel Lives are all excellent examples of cards that double token generation, but they are all quite monetarily expensive
My Background For a bit of background about myself, I started playing Pokmon around Burning Shadows, and have played in a handful of Regionals/ICs, but had not made Day 2 until this most recent weekend in Portland

Gengar (Chilling Reign 057/198) 2022 Trick or Trade Bundle Umbreon (Obsidian Flames 130/197) 2024 Trick or Trade Bundle Gengar (Lost Origin 066/196) 2023 Trick or Trade Bundle Mimikyu (Paldean Fates 037/091) 2024 Trick or Trade Bundle Pikachu (Paldean Fates 018/091) 2024 Trick or Trade Bundle Pikachu (Paldea Evolved 062/193) 2023 Trick or Trade Bundle Darkrai (Obsidian Flames 136/197) 2024 Trick or Trade Bundle Mewtwo (Brilliant Stars 056/172) 2022 Trick or Trade Bundle Flutter Mane (Temporal Forces 078/162) 2024 Trick or Trade Bundle Pikachu (Evolving Skies 049/203) 2022 Trick or Trade Bundle Teal Mask Ogerpon Scream Tail Top 1: Gengar (Chilling Reign 057/198) 2022 Trick or Trade Bundle ($0.52) This Gengar from Chilling Reign set marked 057/198 with the Halloween / Trick or Trade stamp is one of the most sought-after Japanese collectible cards in the Trick or Trade bundle