Many ways to earn bitcoin, mostly people earn by signature campaign because that doesn't need any skills. But signature campaign won't give you big amount of btc.You should do trading to earn big because only trading can give you good profit in quick time.
I know we dont require any skill for signature campaigns but we need to have some good english and must be constructive in posts but i also dont consider signature campaign as main earnings of bitcoin,either you need to be expert in trading or have other skills for that.