Needless to say, you need an adequate budget to spend some quality time in Shanghai. Prepare a budget for your tour as the second step in your planning process. Estimate the costs that you will have to incur for accommodation, travel and transport (including the air ticket fee), meals, souvenirs as well as the ticket fees for various activities that you have in mind.
This doesn't need to be an exact estimation, but a rough estimation would serve the purpose. You may ask a friend who has previously been to Shangai about the costs or even search for the cost information on the internet.