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.
Short-term investments must be monitored properly, because profit targets will be taken in a short period of time. So it is necessary to read a good candle chart. Without doing a good analysis, trading is only done guesswork and the same as gambling.
Portfolio diversification really needs to be done, and what I personally think is mandatory is bitcoin and Ethereum, these two coins must exist and for other altcoins you can choose the best on the list of the top 10 coinmarketcap or coins that you think are the best.