You can't earn big amount with that small capital because if you want those big profits then you should be able to provide big capital. If you want to grow it slowly and much safer way then you should buy bitcoin with that $25 and keep it and wait for the price to pump and there you go! you earn money little by little. Don't be mad if you just earn a few cents because you only have small capital. Provide bigger amount to get bigger profits.
You are right, but most of us are without big capital, or we don`t wish to spend more on some investments, not to spend, to risk more then that. Earning few cents here and there is a good thing, not just that you are making some safe profit, you also learning how to make money. In the end its principals are the same, with 25$ you can make 5$ simple and without big risk, same math is with 25k and trying to make 5k, but how can someone provide bigger amount, that is much easier to say then to be done.