Not necessarily interactions with each other but these are my starter recs (note: I'm actually still working my way through reading this full list so I haven't vetted every single one for quality)
Batman: Year One (collects Batman 1940 #404-407)
Batman: The Long Halloween 1998 (self-contained story)
Batman: The Knight (self-contained story)
Batman: Dark Victory 1999 (self-contained story, sequel to long halloween)
Batman and Robin: Year One 2024 (self-contained story, ongoing)
Nightwing: Year One (collects Nightwing 1996 #101-106)
Batgirl: Year One (self-contained story)
Batman 1940 #408-425 (first appearance, main time as Robin)
Batman: A Death in the Family (collects Batman 1940 #426-429)
Batman: Under the Red Hood (collects Batman 1940 #635-650 and annual #25
Batman: A Lonely Place of Dying (collects Batman 1940 #440, New Teen Titans 1984 #60, Batman #441, New Teen Titans #61, Batman #442 - his first appearance)
Red Robin 2009 (requires some background knowledge but important to his story especially in fanon spaces)
Detective Comics 1937 #647-#649 (first appearance)
Batman 1940 #567 and Detective Comics 1937 #734 (first appearance)
Batman and Son (collects Batman 1940 #655-666)
The Boy Wonder 2024 (self contained story)
Robin 2021 (self-contained story, requires you to know several outside characters but a personal favourite of mine)
We Are Robin 2015 (self-contained story)
Robin War 2015 (self-contained story)
Batman and The Signal 2018 (self-contained story)