The thing with bitcoin is there was a period when it was new and very few people knew about it, like most "investment" vehicles, that was the time to get in and take a risk. Basically, you have to get in before everybody catches on to it. Now that there are so many cryptocurrencies to choose from and the concept of crypto trading/investing is quite mainstream, the possibilities to earn big money easily from buying bitcoin are now quite small.
What I'm looking at now are space industry stocks. At the moment I'm slowly building up a stake in Virgin Galactic, and also trading in and out as I do it which is making me about a 10% profit on my capital each month.