Well when buying btc you already made an investment. Just think about all those people that bought btc when it was out at 300 usd a couple years ago... probably just keep buying is the best choice
You also have to limit yourself, buying all the time is just like putting all your money in bitcoin, that is a risky move as bitcoin is not
guaranteed that it will continue to rise, think of the risk, so never go all in but instead invest what you can afford to lose.