A dream that you win something can be a message from your unconscious that you have the ability to be successful.
Winning at an athletic event in a dream can be your unconscious mind’s way of rewarding you for something good that you have done in waking life, but which you may not have consciously thought about.
Winning the lottery in a dream could be be showing you the results of working hard, how your life would be if you were rich.
Winning dreams can also be simple wish-fulfillment dreams.