If you ever find yourself gambling with people's money it means that your gambling addiction has become uncontrollable and this might put you in lot of trouble. I don't even advice you to use anyones money to do whatever you think is better and profitable than gambling be it crypto trading or forex trading. In a situation where you gamble with someone's money without thinking of you the consequences at that moment is the addictive phase of gambling no matter how desperate you are there are some lines you shouldn't cross, this is one of them
You said there are some lines someone should not cross, no matter how desperate they are. Do you know what being desperate means?
When you are desperate for something, there is nothing that you can't do at that point in time in order for you to feed that desire or whatever arose from that desperacy in you, so saying there are lines someone should not cross when they are desperate is, in my opinion, impossible.
The person should not even get addicted to gambling in the first place because once they get addicted, it's hard for them to control what they can do and what they can't do.