If you’re fairly familiar with the characters, I would suggest just jumping into an event like Infinite Crisis (or any of the various crises guess). Now, not all the tie ins, because that would take years to do. Just read the main series. Then you get to go to 52. 52 is one of the best crossover series on here, and once you’re comfortable with that, you’ll be ready for anything DCU has to throw at you. You’ll be introduced to a bunch of smaller characters who you can then explore. And once you e done that, you’ve officially entered the DC rabbit hole that many of us have been (joyfully) stuck in for most of our lives. Once you’re there, just pick a series, any series, and go with it. Don’t worry about continuity, but if something interests you, then track it down and read it.
Have you watched Justice League Doom or read Justice League Tower of Babel. I think those get into dark aspects as well as include numerous characters you like.
I watched that and I read Tower Of Babel. I started on year one Batman. Decided to start in the mid to late 80s, post crisis
Outside reader coming in: Sees the list of comics and think OMG, how can I read all that? I’ll never catch up!!
Reader already reading DC: Wish they would stop rebooting comics. Seems like everything I read and get invested in is wiped away a year later.
I just pick someone and start reading!