Personally when i was using Poloniex about a week ago ( i still use,lol it is a great market ) i have found that predicting ethereum is pretty easy,
at least for me.
But bitcoin price is higher,so for example i cannot trade bitcoin while having really small deposit ( on poloniex,dunno about other ex )
I have make lots of trading also on poloniex and the main coin that I've traded was Ethereum and it was amazing to see how often the exchange rate was changing and the main role was bitcoin price, as higher the bitcoin price went the lower the exchange rate was.
price changes,and how it moves,related to bitcoin.
The spread was also great,i really recommend Poloniex
I have learned about ethereum very long time ago when the price was 10% of the price that is actually now, and wasn't much interested to invest in altcoins because it was risky for me as i didn't know how to trader etc, but through the time I had positive balance because of ethereum.