I think the best coins to get involved with in 2018 are going to be privacy coins and coins that focus on faster transactions with big block sizes and perhaps even zero fees. Basically the things that bitcoin struggle with other coins will pick up the slack and these coins will do quite well in my opinion.
Following on this, I feel like DeepOnion and Komodo have large growth potential, both privacy coins (although deeponion is a much smaller market cap), so I'd try either.
I have been hearing a lot about these two altcoins as of late. I think, with enough study, it would be worth it to give it a try. On the one hand, I would suggest the usual powerhouse when it comes to altcoins, I would say that Eth and Waves for long term investments. LTC, Ripple and Stellar for short term investments. The altcoins on my list are some with the best possible chances of success despite the market generally going down right now, which is casting a lot of fear to a lot of cryptocurrency followers.