Just like Q, you gotta think carefully for yourself on this. But after years of learning my lessons, I believe in sensible diversification. And it depends on your personal circumstances (how much time you have, how much income, how much net worth, how much risk).
For a simple workfag with limited money, I like a little gold and silver. I like a little bitcoin. I like enough cash on hand to get you through a month or two. And I like the Dow. Because Trump likes the Dow.