Okay, so there are couple available options. Keep in mind that this is not a financial advise so buy/sell cryptocurrency on your own risk.
Of course, I would suggest Ethereum as #1. But don’t except to double or triple your investment. Expect 1.2–1.7 times growth.
Other interesting projects to look at:
Factom
Steemit.
It has an interesting concept behind it and might have solid growth in future (long run)
Stratis. Interesting platform, affordable price, and good growth perspectives.
NXT
It’s on hype right now, and many people find it attractive, but I don’t like that much platform behind it.
Black Horse of the game: IOTA. It was introduced today on ICO, so far it’s not available on Poloniex, only on Bitfinex
I don’t know if it’s good or bad investment. So far it got not bad initial investments, but meets strong resistance and fails to get stable support line. But it’s first day.