The wisest spending principle for ordinary people: buy only what has been proven by the entire world. This is not blind brand worship; products sold globally are scrutinized by the laws of dozens of nations, billions of consumers, and countless media outlets—any defect would have long been exposed. The whole world is conducting trial and error for you; why spend your own money to fall into traps? The wealthy can afford to pay for lessons; ordinary people can only afford to pay for certainty.