Is it cost-effective to buy Octopus for a one-day tour in Hong Kong or a one-day ticket?

One-day ticket is to 65 yuan, so you can sit anywhere within 24 hours, but it is difficult to fill 65 yuan within 24 hours, unless you have been changing trains on the MTR for 24 hours. So buy octopus. It can be used by MTR, buses, ferries, convenience stores and tea restaurants. You can buy it at the subway station and airport express customer service center after you arrive in Hong Kong, or you can buy it in advance. I bought it in Pocket Hong Kong before.