I am applying for a tourist visa, do I need an invitation from a Chinese Citizen?

I am an Australian citizen working in Costa Rica. I have previously lived and worked in China. I want to visit several friends in China for a 2 week stay in December from the 17th. I will spend my time between Xiamen and Ningbo. For the tourist visa application, do I need an invitation letter from a Chinese citizen? Are hotel bookings sufficient? What other options do I have?

Lloyd Brown