Hi Therick,
I'm quite new to cryptocurrency (less than 1 month), but I asked myself the same question than yours. After thinking about it for a while, I went for:

• Ethereum: Very big growth (400%) this past month so I dont think it will go up again very soon. But still, it has a huge potential as a platform used by other apps
• Swarm City: the price is very low for the moment, since the launch of their MVP. Its not very impressive for the moment, but for me, that app can have a huge success. Basically, it's a decentralized craiglist which help entrepreneurs to find customers and vice-versa.
• Lisk: another platform, as Ethereum. Their main value proposition is the sidechain feature and the fact that their SDK will be based on Javascript, a well-known langage by devs.
• Steem: obvious pick :) I like the altcoins with a real product you can give a try - not just a "concept" or a "whitepaper"

You should do your own researches as well. I think it's important to invest in something you understand and believe. Best way to play the long term game without worrying too much about the BIG daily fluctuations of crypto currency prices...

Good luck !