What are the differences between being a disciple of Christ and a keen follower?
This is an interesting question. What makes you distinguish between the two in the first place?
I suppose if we start with the premise that they are two different types of people, then I would probably contend that a disciple is also, but not exclusively, a keen follower. But a keen follower is not quite (or yet) a disciple. Maybe keen followers are watching from afar? They are eager to see God work, but they themselves do not participate. They are fascinated maybe, but not yet ready to commit to the life.