Never do things out of spite after a breakup

Sleeping with her friends, getting rich, or changing yourself specifically to make an ex regret leaving you is not inspiring, it is handing your power over to someone else. When your motivation is revenge, the person you are trying to hurt still controls your behaviour. Whether you are going with the wind or against it, the wind is still deciding your direction. Fabrizio Rausa puts it plainly: if you became wealthy because she hurt you, you are telling the world, and her, that she is the reason you succeeded. That does not make her respect you more. It makes her think you are foolish. Do things because you genuinely want to do them. Get rich because you want to be rich. Spend time with her friend because you find her attractive. The moment the true motivation is spite, things will almost certainly not work out the way you hope.