Buying bus tickets for Xiamen from Shantou?

I would like to buy 4 bus tickets leaving for Xiamen on November 29th morning for 4 persons.
Do I need to buy in advance(November 28 night) or can I get tickets at the bus station.

1. What is the name of the station, and how much is the taxi?
How long does it take?
How often is the bus? every 30 mins?
Thank you

Bea from Malaysia