What is functional obedience?
Functional obedience is not the traditional set of commands; instead, it is obedience that coaches your dog toward being a good citizen and companion. For example, most dogs do not need to walk in heel position, but all dogs should walk without pulling on the leash. These are two different exercises taught in two different ways. I’ve seen highly trained competition dogs that pull horribly on the leash at home. A formal heel is not a functional skill for most dog owners, but loose leash walking definitely is.
So decide for yourself what commands and skills are important and focus on those. You might also want to teach your dog tricks or higher level skills, which is great for their mental stimulation (all training is mentally stimulating), but the foundations, the commands and skills that you incorporate into your daily life, are what really matter.