I was thinking of buying ethereum now at a price of $ 300 and I want to hold it until the end of 2018.
what do you think?
I think that buying ETH is a great decision, particularly at the current price. But I would say hold it longer than that if you want significant price increases. 2018 hasn't been great so far, and there's no real indication at the moment that prices are going to increase any time soon.