Of course buying Ethereum now is not smart. THe trend is bearish so there are big chances that the price will move down again.
It's already below 100 so it's a good buy if you're holding for long term. It doesn't matter if the price could still go down since eth would likely get above 500 usd in months or next year. Again it will depend if you're willing to go long for this to be a good idea.
Choosing ETH for long-term holding now is a genius idea. It's a great coin with huge potential and we can thank heavens that prices are so low now, it's unbelievable.