In the Theravadin school, we do not say Amitabha in greeting or follow any teachings related to him. We just follow the teachings of the man known as Siddhattha Gotama who through his own efforts became an enlightened person. After his enlightenment, he began to be referred to as Shakyamuni Buddha. More often than not we usually just greet each other with Namo Buddhaya, since it means salutation to the Buddha.
Amitabha came a good number of centuries after the Buddha passed away, the oldest recorded scriptures in Chinese referring to Amitabha was around 180 Common Era, while the Buddha's death is reported to be somewhere around 400 Before Common Era plus or minus 20 years.