Buy bitcoins and keep them safe in wallet as price is expected to go higher in future or else you can also invest in some altcoins at cheaper price and if price pumps then you can make huge profits in quick time which will also grow your bitcoins.
Bitcoin has a massive amount of potential gains that it can realize due to the demand coming from people trying to escape the governmental system. From that point it's indeed a great investment.
Altcoins on the other hand are pure short term investments for people looking to bank on a potential pump, but the whole point is that they can also go in the opposite direction equally as fast.
That's why it's important not to discard the extreme risks involved in altcoin trading. It's something I see happen quite frequently where people only focus on the positive side and thus completely ignore the risks.