Joining signature campaign are indeed a good source of bitcoin not really high in terms of profit but theres no risk just do what ever rule in that campaign, and for me trading is really a best source of bitcoin it allows you to make your money doubled for just a weeks if youre tough enough though its risky but the return is really high.
Yes signature campaign and trading are the best ways to earn bitcoins and if you are good in trading then you can multiply your bitcoins in very quick time and no doubt trading is risky but after gaining knowledge it will become easy for you to analyze the charts and price movements.