The best investment at a moment would be to buy as many bitcoins as possible and hold them for the future as apart from that I don't see any good place to invest my money from where I can earn huge returns on my investments which is only seems to be possible with bitcoins.
Bitcoin's price is so much hyped according to me at this time and investing now is quiet risky in my opinion, I would recommend investing in monero as it is still very cheap and it's use is increasing day by day on darknet and it is following the same story as of bitcoin.
Yes i also think that investing on bitcoin now is quite risky because the price of bitcoin is getting stabled and there is only two things that might happen its either bitcoin will continue to rise or bitcoin will go down to its low price. So to be safe, it is best to just wait and just observe the market before purchasing any kind of coin.
It did fall earlier this year to about ~$800, that would have been a good time to buy and to sell at ~$1200 as it is now. Unless there's an extremely large hack found, then there's probably not too much of a problem with the currency falling in value as it'll generally rise back up afterwards.