@AlexanderKnox is doing the lord’s work in terms of compiling a database of recommended reading lists. That’s super valuable for DC fans in general.
In terms of my personal taste, I would obsess over vintage ads and commercials from comics and toys, and OMG vintage DC T-shirts! I have spent an embarassing amount of money on vintage T-shirts. I have an original “Revenge of the Jedi” shirt I am very proud of.