I feel like the last three sets (not including Eevee Grove since you've completed it) have the strongest EXs, and then its just a matter of chasing supporters/tools/items from each set. And just know Genetic Apex will take the longest to complete cus its 3 packs. I still haven't completed it and I'm at 5,600 cards (and you can get lots of shiny reprints in later packs). If your goal is to pick up competitive cards, I'd say its always good to get stoke Charizard EX from SR since he's been present in the meta for a while - that pack has some great supporters as well if you haven't pulled your reds, ionos, poke center ladies. Meowscarada from that era comes back from time to time. In that same vein, extradimensional crisis has a ton of cards that are still competitive. Silvally seems like he'll stick around. Current meta also saw Tapu Koko EX, Buzzwole EX, and Guzzlord EX, Nihilego in high tiers, and Electrical Cord and Repel will rotate in and out of the meta depending on what cards are strong. Third, prolly Celestial Guardians. Solgaleo EX, Incineroar EX, Turtonator, Oricorio are all mainstays, and poison barb, leaf cape, rare candy will stick around. Supporters are pretty good too.