My gf is break-up with me, but how long should I wait, to DATE?

Just take your time and don't rush into anything right now. Enjoy this time to yourself to discover what you want to do and if she were to come back you can see if you want to work it out with her again and you don't have to worry about having that other person there and worrying about hurting them if you chose to get back with her. Believe it or not i know it will hurt for a little bit but you will also have a chance to grow a little bit and get to see how much you care or even love her. If you get into another realtionship right now it will probably end badly because you haven't had a chance to heal from your your ex. Good luck to you