That's what we called friendly gambling or friendly game because there is still pride involved with it. Even without money, you can still gamble as long as there is something on the line, even if it is just a simple command, like if you lose, you'll do this. The feeling with it is not also the same with money on the line because this is more fun as both of you will be doing it and friendly mocking each other. Though this still depends on others views, we are not the same.
But it's going far to be off topic from the context. You have money and you can gamble with it. You have no money and you will not able to gambling. It's all related to the gambling. I don't even care what you have stated above was about friendly game or whatever it is but it's not related to the gambling.
Money is the main thing required in gambling as people are willing to doubled or tripled their money through putting it in the casino or sporsbetting.
People without money can't play casino. Money is the main purpose here in doing gambling. I believe you understood it.