I read a blog post about Kaiji and the person wrote that Kaiji is an evil series that promotes sin and a bunch of other things. Yes, the characters lie and betray one another for personal gain and greed. Yes, some characters have died or are subject to inhumane human labour. Yes, some characters have lost limbs as a result of losing a gamble. Does the manga promote crime and murder though? I fail to see it.
It’s a work of fiction. Am I as a reader going to go and start deceiving people for my personal gain because I’ve read this series? Of course not. What I got from the manga is an intense and exciting reading experience. Most of the time, you read manga for entertainment. Am I a bad person for reading this series because some characters have died and other characters are in terrible life situations? What series doesn’t have something like this.
Kaiji Itou is a man thrown into unfortunate circumstances. He’s not particularly smart like Akagi, for example, and sometimes loses his gambles. What strikes me about him is his perseverance and desire to overcome his obstacles. This is why many people became interested in the series. I am caught up on the manga and do not think that this has changed. Kaiji still has obstacles he needs to overcome but he has been vigilant and cautious in Part 6 of the manga.
At least in my experience, I feel motivated after reading Kaiji. Seeing Kaiji so determined makes me want to do something. This “something” can be as simple as getting out of bed. Sometimes I look at my life and think, what would Kaiji do? He wouldn’t give up like this. There are many inspirational quotes in Kaiji.

As for the Tonegawa series and comedy spin offs, I think they are fine as long as they are separate from the Kaiji manga (and they are). I’ve read the spin-off manga and watched the spin-off anime. I know that spin-off Tonegawa is not the same person as Tonegawa in the Kaiji series. That being said, spin-off Tonegawa does not change how I view Tonegawa in the Kaiji series. Tonegawa is a separate series and should be seen as such.