I'd recommend getting a number of books and magazines:
The Old Judge book is a must have:
https://www.net54baseball.com/showthread.php?t=337137
Lew Lipset's Encyclopedia is still an outstanding resource, if you can find a copy:
(The Encyclopedia of Baseball Cards, Volumes 1, Two & Three Combined)
If you search around, I'd recommend picking up complete runs of
VCBC (The Vintage & Classic Baseball Collector Magazine)
and
Old Cardboard magazine
https://oldcardboard.com/subscriptions.asp
Cheers,
Steve