Where can I buy shanghai sightseeing bus tickets and what is the price?

You can take it at Xin Tian Di Bus Stop. The exact boarding site is located at No.222, Hubin Road. From your hotel, just take a taxi to there. And it costs around CNY 20. After arriving, you can easily find a ticket booth. Or just pay the cash to the driver. The 24 hours ticket is CNY 30 per person and 48 hours ticket is CNY 50 per person.