People
People come first because they are the only part that compounds. Systems decay, frameworks get replaced, and the roadmap you defend today will be rewritten. What remains is the judgement in the room — and judgement is grown, not hired in finished form.
So I treat mentoring as the actual work, not the overhead around it. If the team ends a year abler than it started, the systems tend to follow.
In practice mentoring 12+ Python and ML engineers, hiring for density over headcount.