Both movies and comics! If you’ve not watched it before, the Justice League animated series has PEAK Lex Luthor content. He’s not “babygirl” like in the Superman movie, but his character is so well written and the story is just so deep and peak. Smallville Lex is also really fun (if you liked the Superman movie Lex, you’ll like Smallville Lex.)
Though! I will say the best way to get into DC Comics is by the Justice League animated series (and Young Justice too) Justice League has such a big cast and highlights a lot of more “unknown” and unique characters apart of the DC universe. And from there you can start digging into the silly guys comics