Warren Buffet is an interesting case, because his approach seems largely to consist of ways to reduce the N of what he is considering: choose a few bets, bet big, hold for the long term, choose bets where you already understand the market. Sampling, rarely recalculating and selecting subsets of N where the related data is already in cache are all well-understood techniques for addressing computationally-hard problems.

He's done a good job of avoiding expensive mistakes, not being pushed to invest cash in something marginal just because it's sitting there.

Half the battle is not doing something stupid.