Dubai is one of the busiest airports in the world. Almost every flight that goes from Asia to Europe or America has a layover in Dubai. I was flying out from Lithuania to Indonesia for a conference and had a layover of around 12 hours in Dubai. Since my layover was overnight I could not experience much of Dubai's culture as most things close early. I did however get a chance to explore the amazing nightlife of Dubai and also catch the sunrise at the pristine clear Dubai beaches. In october specially the weather is nice to go to the beach and enjoy the sunrise.
How much you spend depends on what you do. Dubai is a city of extravagance and style and its very easy to go overboard in your spending. I don't like a flashy culture too much and prefer nature anyday. I spent mostly on drinks, some food and taxi rides (Metro closes in Dubai at night). The best thing is to get a taxi and keep the same driver with you for the night. It will cost you around 100-150 USD to cover all the spots mentioned in the itinerary with a taxi. Keep around 200 USD for drinks and food at the various places mentioned by me.