I’ve been thinking a similar question quite a lot and if i could have any pokemon set graded but nothing else it would be original 3 trophy pikachus, obviously out of the budget for both me and this thread but those are imo the peak of artistic, historical and monetary value combined
At this moment I would personally choose Crown Zenith psa 10 set. Awesome set, amazing artwork, still super cheap even for all the chase cards and youll save yourself 25k. As for WOTC era a psa 10 Gym Heroes set would be very cool to own. The Sabrinas Gengar and Blaines Moltres are great artworks to own. Especailly in gem mint conditions. If you want to really dig in you can try going for a Jungle No Symbol PSA 10 set of the 16 No Symbol holos. Super rare, super low pop and super cool to have!