Ethereum is one of the strongest cryptomoedas on the market, in my opinion it has always been profitable to invest. But there are several strong altcoins that you can invest such as, Dash, Monero, Litecoin and Waves which is now coming in with a good value in the market.
But if it is to invest, expect it to be lower in the last ones. The strongest altcoins are going up the BTC values ​​a lot, so they will soon have a brief low, at which point you buy.
Now if the purchase is in Dollars do not worry about when to buy because the tendency is for the values ​​to rise more and more.