I'm a professional horse racing handicapper.
and I'm a degenerate gambler. what a coincidence. I do love that equestrian performance sport.
When was horse racing invented?
It's the most ancient of all sports . It has been around since time started and the sun started to rise in the sky. 
How much money is generated from gambling on horse racing?
More then you can imagine. In 2008 alone it generated over 115 billion. Yes billion. You must be rolling in the money with your handicapping skills.