Is there a cable car that goes to Gulangyu or only ferry?

Yes, you can take a cable car from Sunlight Rock to Birds Garden.

The all in ticket costs CNY 100, and it includes Sunglight Rock, Shuzhuang Garden, Bright Moon Garden, Organ Museum, and International Lettering Art Gallery.

You can book the ferry ticket at the offcial website of Xiamen Ferry Co., Ltd. But the booking system only has Chinese versions, so you may ask your Chinese friends for help. Or just buy the tickets when you arriving there.

Hello Gloria, above in the text it says the all in ticket is 80 yuan and here in the answer you say its 100 yuan? how much does it cost?

Hi, dear! The ticket fare is CNY 100 nowadays. May you have a nice trip! :)