To dream of winning the lottery represents a lot of power or resources you feel you've gained through chance. You may feel you really lucked out. Something good may have happened to you and you can't believe how wonderful it is.
To dream of buying a lottery ticket may represent your hope for good luck with a big opportunity. Taking a chance with something good that you hope happens.
Example: A young man dreamed of winning the lottery. In waking life he landed a really good job that he wasn't expecting at all.
Example 2: A man dreamed of seeing himself being told he won the lottery and not believing it. In waking life his father had took all his money and refused to give it back. When he heard his father was dying he felt like the luckiest person alive.