Gambling is a ordinance in SimCity (2013).
Walkthrough to Gambling
The first thing to a gambling city you should know is that it is advised that you have another city in the region before starting a gambling city although it is possible to do so without another city in the region. Also, it is extremely advised that you have a railway and shipping access to your city.
If you meet those requirements then you are ready to start a gambling city. The first step is the same as a normal city by drawing out a residential zone and a commercial zone but not a industrial zone. The reason for that is that you will want to combine gambling and culture into one city as tourists will gamble more and tourists do not like pollution.
After you have started with a normal city and put in basic services (if you cannot send sewage and garbage to other cities and import power for whatever reason, send the garbage and sewage into a small corner of town away from the other parts of your city and use clean power sources like solar and wind) you can start with your town. You would want to do is add a department of transportation and try to have as little traffic as possible around your city as that again does not agree with tourists. You will also want to build a railway station and may be a Ferry but this not required to make a gambling house.
You are now ready to make a gambling house as long as all the requirements from above meet the requirements as listed above and a sufficient police force as gambling attracts crime to your city. Put the gambling house away from pollution and near your railway station and (if possible) police station. Then edit it toward the type of wealth your trying to attract (you can find what types in the description of the attachment).
Be careful however, because introducing gambling into your city will increase crime rates dramatically, and overload public transport. I recommend that you improve your security and transport infastructure extensively before opening a casino or gambling house.