My answer is different...
Your circle of competence depends on yourself. i.e John Templeton travelled around the world and he was comfortable hunting bargains around the world. Charlie Munger is a ex - lawyer who needs to think everything (Politics, Science , Business) to solve a legal problem , hence his was a multi disciplinary way to look at Business. Martin Whitman was a vlulture invester , so he invest in distressed securities.
But lot of us will do better, if we just identify the bargains , Hire the experts and ask them to thrash you out your analysis. (Bruce Berkowitz way).
Vishnu