(. ..)
Because participating in signature campaign is not for all members and you need to know that you need to also to be qualified before you will get hired for that job.
And for his rank it is impossible for him to join only few campaign accepting that rank.
Actually there are lots of ways to earn bitcoin. You can invest your money to some projects in here and the only thing you need to learn is on how to recognize a good project and to study if you can really earn when you invest to that, there is also trading wherein you can buy some tokens and hold it maybe for a long time or a small-time only and it depends on you when to sell but you should not do panic selling because it will be a big loss if you do that, buying high price and selling it low is not a good decision to make. And just like what you have stated, you can join particular signature campaigns here by promoting that and that particular project will pay you for the tasks you have done.
Trading and the gambling is the best for me, I enjoy those two things, actually they are slightly similar considering that, those two have risk the one is 50/50 and the one is based on your knowledge on the market and personally, I love risk and for me as long as you are doing it right you will never lose on those two. You might lose on gambling blindly but, if you are going to do it right for example, betting on sportsbet or playing poker you might lower the losing chance there.
Just a tip: When earning make sure you will save some. Hold and trade is the best strategy, and sometimes gamble to have fun.
There are so many strategies you can learn here, you just really need to study on your own or if you have someone who really good at trading or gambling, maybe you can ask for help to teach you how to do that particular stuff for you to earn smoothly. Knowledge and patience are important here since the profit is not that easy to get and can get with just a blink of an eye.