This is more about trading than gambling, you can't make a profit if someone else doesn't lose. When it comes to gambling, this can only be applied only on poker and maybe on a few other PvP games (bet there aren't many of them), all other games are players vs house. So we can see a few players winning while the house is suffering, but how often that happens?

Clear expectations about gambling & trading are to expect the unexpected. We can make some profit, but we need to be aware that we can lose as well, it's why it's important to be responsible. Never risk too much, it can backfire so easily and pretty quickly.