At the end of 2018, Ethereum is likely to go up, but now It is successfully falling down, so it is not worth investing in this cryptocurrency yet.
I think that when the exchange rate is low, the investment in ETH is very reasonable. Your advice that the exchange rate is low should not be invested but still optimistic about the exchange rate of ETH in the future is totally unfounded. So my point is to invest in ETH at the moment.