I'm only a few episodes in, but I'm getting some strong Kaiji vibes from the series. Deadbeat loser of a guy with gambling addiction falls prey to nebulous underground organization running crazy gambles modeled after simple games? That's both the series in a nutshell.
Though, Squid Game seems to be going for more shock value and emotional punch than the psychological desperation that permeates Kaiji.
I bet if you like one, you'll like the other, so if you want to scratch more high-stakes gambling iches, I can heartily recommend Kaiji.
There is no shame in not knowing; the shame lies in not finding out