Should your primary keyword always start condensed and be extended into overlapping long-tail with secondary keywords?

Still a newbie here, so bear with me.

So, if my service was life coaching, could be keywords be set up something this to get further credit for the primary kw:

primary: life coach

secondary: hire a life coach, life coach online, how to find a life coach

Or if you lack authority, is it better to start with a long-tail keyword as your primary and simply use semantic variations or related ideas as secondary keywords?