Can you please tell me the best way to get from YangJiang to Chongqing?

Well, there is no train between Yangjiang and Guangzhou. So you are suggested to take bus from Yangjiang Bus Station to Guangzhou Provincial Bus Station. After arrival, you can walk to Guangzhou railway station and take train there to Chongqing.
Bus from Yangjiang to Guangzhou Provincial bus station is available from 06:10 to 21:45, with an interval of about 30 minutes.
8 trains are available from Guangzhou railway station to Chongqing North from 09:57 to 18:50. The ticket price is CNY737 for soft sleeper, and CNY414 for hard sleeper.

Thank you very much Sophie!! I was actually planning to take an airplane to get to Chongqing. How would you plan your trip from YangJiang to Chongqing? I read that the best thing to do is to the to Guangzhou by bus. Would you recommend that airport or is there a closer one (Zhanjiang, Macau...)?
How would you plan your trip to make it as fast as possible?

Zhanjiang Airport is the nearest one from Yangjiang, while Guangzhou Airport is the best choice, because it operates more flights to your destination.

You can take a direct long-distance bus from Yanjiang Bus Station to Guangzhou first and then take a taxi to the airport to catch your flight.