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.
I think XSPEC is a great choice with a low market cap. It has gained a lot of momentum and the techonology behind it is incredible. A front runner in privacy.
I also recommend ZCL, 10x less the valuation as Zcash (it's the same coin) and soon to been a bitcoin hardfork with less than 200m valuation IMO.
Happy 2018