You don't have to own a whole coin but it's also a misconception that you can also accumulate Bitcoin by spending $10 per month. What do I mean; you'll often see newbies here (I also responded to a relevant thread a while ago) with a budget of $20 per month, to buy Bitcoin. In these individuals, it has been carved into their mind that Bitcoin is a quick get-rich-quick scheme in which their $20 will flourish. What I'm trying to say is that the DCA method is great, but only in cases there's a realistic budget, and not something as ridiculously low as $10 or $20, because we all know that such amounts won't lead to any significant returns.
People should know that they amount of money you invest on Bitcoin will determine how the profit will turn out. Anyone who believes that buying $20 worth of Bitcoin monthly will make them get rich quick is deceiving themselves. With the worth of Bitcoin, buying such an amount monthly will take a long time to bring high returns. Anyway, it is better to buy with the amount you have than not investing at all. So people with such amount can still buy but they shouldn't expect to become rich overnight.