Which is the best ticket for a 2 day trip also using the Airport Express

Hello, what is the best ticket to purchase for a 2 day stop in HK, while also travelling from the airport to Mong Kok. The following day I will travel from Mong kok to Tsim Sha Tsui and back to Mong Kok . Then the following morning I will return to the airport. Many thanks for your help, H