Bitcoin is not the only cryptocurrency you can invest in. I have made some recent research and i have come to the conclusion of some project i have been buying into recently
1. Cardano
2. Stellar
3. Oikos
The first two coins do have very good future potential, although the Cardano development team looks very ordinary nowadays. I haven't heard about the third coin (Oikos) and therefore I am not going to comment on it. ADA and XLM are good options, if you want to invest in coins outside the top-10. Both of them went up sharply during the 2017 boom, and then went down even more sharply during the 2018 bust.