Putting all your eggs in one basket and looking after its price all the time will only cause you a lot of stress. You better divide your funds at least into three or four and buy potential coins which are worth holding and has a huge chance to reach a good value in the future. Bitcoin and BNB are other good choices.
It is smart to diversify your portfolio, but don't expect it to help you avoid losing value during a down market. It is also much more difficult to keep track of several coins than to do it with one coin. For long-term investments, this is easier to do, but if this is a short-term investment, then constantly monitoring several coins will be very tiring. If the portfolio consists only of Ethereum, then where Bitcoin can definitely be added.