I think those are high potential cryptocurrencies for 2018 : waves, 0x, stellar, pundi x, pivx and oax. I think for 2018 and next years, unpopular coins which has very low market cap are very risky because they most fail because of lack of money.
The market price change every time and it's hard to speculate a certain coins which have a huge growth in the incoming days. Although we consider some coins that have potentials, but it is not enough to say that it will surely pump.