Just stay away from ponzi scheme or something like that, you might build your own business, or investing on trusted scheme like gambling investment, lending company or some kind of that, you must check the reputable of the company first due to the so many scam site out there,
i hope you find your way
The important thing is the secure of the investment. I agree with you. After that, check the company have potential to give profit or not.. Although it secure but also must profitable.
Yeah everyone likes to have a secured investment. If you are in need to earn 100$ from bitcoin the highest possible methods are trading and gambling. You can try trading but it takes time to earn $100 if you don't have big capital.
Let`s be honest there is no safe investment. Everything is risk, every time we invest in something we are not sure that we will earn.
I don`t know what people think, its not easy... For me everything is gambling, you can say what ever but in trading its easy to lose everything like in gambling.
with $100....mmmm, let's see....buy some cocaine, work on it a bit to make it weigh, and than resell it...easy 50% return on investment...that's the only way to make some fast profit with $100
An even riskier method is this :
Go to a physical casino (not a virtual one), play the black or red on the mechanical (not electronic) roulette and hope for the best...easy way to double your money, but riskier than the cocaine method

Option 3
Is to get more money , at least 4 digits, and a lot more options will appear on the screen...