Gender fluid is a gender identity which refers to a gender which varies over time. Everything else depends on gender fluid person.
some examples of patterns in Gender Fluid people:
Amorgender- where a person gender changes depending relationship are in, whether romantic/sexual or platonic.
Genderflux- where the gender remains the same but the intensity of the feeling varies over time.
Lunagender- where a person's gender changes on consistent, orderly cycle, reminding one of a lunar cycle. The cycle could be as short as a period of days or long as a period of years.
Musegender- A gender influenced by the gender(s) of the characters you are drawing/writing/roleplaying/etc.