Its hard to say what to invest in because anything can go up or down at any moment. With that being said, I invest int he following:
ETH - I mine this in my basement at the moment
ETC - I invest in this
Bitcoin - I invest in this because its relatively safe and accepted more then other bitcoins
Use poloniex to judge what a good fit and risk/loss is best for you.
RE: What Crytocurrentcy would you buy? and what is the reasoning?