If you dream of winning the lottery, it can mean the reverse. Winning the lottery in a dream can imply the converse in real life. It can mean losing money.
In truth, the lottery is like a game of chance. To spend time and other precious resources on uncertainties like gambling, really means you are losing in life. For if you were doing things right, you would not have to gamble.
If you dreamed of someone else winning the lottery, it means you might be benefiting from another person’s gain.