I am growing my bitcoins with the help of signature campaign and trading as I don't have an habit of spending them so whatever I get from signature campaign I try to save them and once I reach to a satisfactory capital I start investing that in different altcoins which helps me in growing my bitcoins faster.
Sometimes due to the amount of profit people can get from trading, even the small amount that people earn from signature campaigns can be significant.
The good thing is that it's supplementary income so the high risks are eased by the fact that you're working with what you can afford to lose.