Any investment is risky. You are safe investing in Ethereum. You can observe the market situation more, and don't miss the market situation. Or you can invest in altcoins you are interested in. Other altcoins are also doing well.
Treat Ethereum just like Bitcoin.
There are also some people who instead of buying other altcoins, just like having exposure to altcoins, intend to buy Ethereum altcoins instead of other altcoins. Because most of their bags are already in Bitcoin.
Yes, that's right. It would be wise to hold ETH, BTC, and some altcoins that are worth to invest. The only problem when you are buying ETH is the high transaction, so much better to buy only when the fees are very low the same with BTC.
You can check this website to track the fees:
https://etherscan.io/gastracker