Best investment is in the stock market. ETF accounts are the best. That is a fact 
the stock market can go up and down at any time, even the stock could go down and do not have a price, you're sure what to think with this investment?
Historically, stock market investment is the best. The stock index will beat the inflation in long term. I am talking about the US stock market. The index tracking ETF is the best, it will beat 80% actively managed funds.
In short term, the price will go up and down, very difficult to predict.