You can't directly earn money from bitcoin since it's a currency and you can't get it just for nothing, You can use faucets and claim there rewards or join a signature campaign on this forum or the like, You can also spend some investment and trade BTC for USD IMO.
Yeah I think signature campaign is the best to earn some good amount of bitcoins as you can earn it on weekly basis without any risk involved into it.
to be honest I can't agree with that because the easier way is to do work for bitcoin with your skills such as programming or something like that
Besides that you can always buy your bitcoins what would be even faster and easier way to earn it though it would cost money for you