"Grow" is a risky word IMO about bitcoin, Bitcoin is not a plant.. No risky investments IMO and people who use the term grow always try to get you into investing in a HYIP or high-risk projects that typically end with scam accusations.
Though risk follows you always when you talk about investing but there are some legit places as well like altcoin markets or casino bankrolls where you can invest your bitcoins and grow them gradually, though they are risky too but not as much as hyips or ponzi schemes.
Yeah ponzi and hyips will never give you anything in return, in fact those are the places where we would loose all our investments, for me the best way to grow my coins is with altcoin trading.