There are no secrets to earning a $100 bucks every week, all you need to do is work and then just buy the equivalent to bitcoin which is roughly 0.1 btc. If you want to you can always join signature campaigns but the maximum that I see that they offer to members is 0.04 btc, which still is not enough to suffice the 0.1 btc that you're looking for. You can also opt to trade or just gamble just to have some extra money on your wallet if in case.
Its good to start with signature campaign and start saving those earnings for the future and once you have reached to a good capital then you can use them in trading altcoins which can help you in growing your bitcoins faster along with the profits if your trade goes in your favor.