invest to hyip. 
One of the best way to grow your bitcoins IF you know where , when, and how much you'll gonna invest. It requires to be a risk-taker though cuz anytime you can lose your BTC but if you are keen in looking for a good and stable HYIP, you'll definitely gain high and quick profit. But as I always say, it's not recommended especially to bitcoin newbies
So for I never see any of these sites survived for couple of years and now a days even these sites are closing with in few days so it simply wasting money if you invest in these sites.