There are some people who like DCA, because they can buy coins in stages. By trading, joining bounties and airdrops, they get rewards to buy Bitcoin or potentially other coins in stages. This is a good method and even better if it is done long before the price of bitcoin is high.
People who plan buying gradually, they may choose DCA. I think it is a good way for the people who have limited funds. But if you have big funds, you can buy many Bitcoin at once. Yes, people who join signature campaign or do bounties, can buy Bitcoin gradually. We have no much money, so DCA can be a good idea.
Diversification is always the right step to increase opportunities for profit. Bitcoin is a safe coin for investment, but remember altcoins are coins that will bring greater profits if you choose the right and potential coins. Do analysis before buying so that we don't suffer losses.
Diversification is okay, it raises the chance to take profits and minimizes the risks. However, not everyone wants to diversify their assets. Some people may invest their funds on Bitcoin or Ethereum only. But other people may invest in varied crypto coins. It may depend on the style of individual investment.