One important distinction between GM stock and casino gambling is at a casino, if the player loses, the dealer still wins. Nobody wins with GM stock.
The cool thing about capital markets, is that investment in production only makes money when there is demand. Investment in production when there is no demand, makes the capital disappear. It's better than Houdini at that. So go ahead, invest. Just choose to invest in producing something people want. It's really very very simple.