Starting Bitcoin investment with little capital will be very challenging mostly if that happens to be the major survival option of the investor. And in cases where the investor plans on using the proceed to solve their needs they might end up selling when the price have dropped just to settle the pressing need of that time.
As experienced investors are there measures that can be imbibed by new investors with little capital to help boast their capital. Some will want to mention patience which I will agree to but in situations where the money is needed to meet an emergency need how to you tackle such situations. Your formula might be a saving approach.
I assume that you are very new when it comes to Bitcoin.
In regards to your concern, I do not think there is an exact "formula" for starters in getting themselves warmed up for Bitcoin.
As we're not financial or investment advisors here, we do not encourage nor discouraging you from getting into Bitcoin or any altcoins.
You should only use your spare money that you can afford to lose when deciding to get into Bitcoin and not going all-in. You must always have some emergency backup funds just in case and a stable source of income to sustain yourself.
BTC doesn't offer any promises or astronomical guaranteed returns as it is subject to market volatility and it can go up or down without warning. Make sure that you always acknowledge the risks and learn how to manage them at the same time.