8 ways you have mentioned can really help you earn money but some of it are just very risky and can also lead to losing your money. In gambling, you can earn but everything there is a risk. Easy money also lose that fast. But if you want to earn bitcoin without investing your money, you can work for it. What you have to invest is your time and effort.
Its indeed speculative but as long as you know how to control yourself on gambling then it won't be a problem because some of you thinks that you can easily earn money by playing various of games without even thinking that you are ending up being greedy. When you have lost something you are willing to do it again thinking that you are able to recover the money you have lose. You think you're earning but you are just doing the same mistake, gambling is fun and its true that you can get something from it but you have to keep in your mind that there is no assurance that you will always win the game.