I need to get from the Guangzhou ferry terminal to Baiyun airport. Best way and cost?

For the ferry terminal, do you refer to the Nansha Ferry Terminal?
If so, it will take you a long time to reach the airport.
First, you need to a free shuttle bus to reach Jiaomen Subway Station of subway line 4 to reach Wanshengwei Station. There you can change to line 8 to reach Kecun Station. From this station, you can change to line 3 to reach the airport directly. The subway fare is around 14RMB.