If you haven’t read ANY yet. Then I’d suggest an origin, either Man of Steel (1986), Superman: Birthright, Or Superman: Secret Origin. They’re all good, my personal favorite is Superman: Secret Origin because it’s the most Silver Age feeling, and it’s still currently treated as the true Superman origin in comics today.
Also I’d suggest reading Man and Superman a 100-Page Special by Marv Wolfman, it’s almost a pre-origin, but it’s excellent.
Other early-in-his-career Superman books you could check out are Superman: For all Seasons and Superman: Kryptonite. Both are set in Superman’s early career, are self contained stories, and are both really good.
If you’re looking for an out-of-continuity Superman story there’s a lot of good one. Superman: American Alien, Superman: Earth One Volumes 1-3, Superman: Secret Identity, Whatever Happened to The Man of Tomorrow.
If you’re looking for something a little more experimental in the Superman realm, maybe try Superman: Red Son. And maybe the Superman & Batman: Generations series.
By the way, this should all be on the DC Universe Infinite app.