Hmm. Depends are u more dc or marvel? Superman Batman and Spider-Man are all great ones to start with. One of my personal favorite books/comics of all time is all star Superman. It’s a great read and I’d definitely recommend it as a good starter book. It’s like ten bucks too and it’s pretty lengthy.
Batman year one and court of owls I find great for Batman and for Spiderman either early Stan Lee Steve ditko 60s stuff or Spiderman brand new day or general tasm are good. Marvels a bit harder cuz they don’t have as many like one off series or books like dc and instead have volumes so it’s a little trickier.