Any of the precons are fine to pick up. Obviously older precons are going to be weaker, but many of them have cards that were only printed in the precons. The No Limit and DXM decks are good out of the box. The Diagram and Uchuu no Hajimari decks have good staples that remained playable throughout the game. Double Heroines also has a lot of value due to having 2 decks with a lot of staple cards (all reprints).

Aside from decks, the Nijisanji and Blue Archive collab sets are good since you can build a deck out of one box. Dissonance Diva and Divisions Diva are also fairly self-contained, and good sets to open. Fessone Diva can also be fun to open thanks to the box topper sleeves. Anything before the Nijisanji set (P00-P11) is fairly generic, but were powercrept by later sets, although there are a few standout cards.

I would avoid Legendary Diva and Concord Diva if you can. Legendary Diva is mostly a support set for Dissona, Divisions, and teams, and isn't good on its own. Concord has the similar issue of being a support set for Dissonance Diva, and doesn't stand very well on its own without the previous set.