Actually, the right time can be at any time, depending on the main target to be achieved. But it's better to buy at the lowest bitcoin price when the market is bear and a lot of FUD is coming.
It means the best time to buy isn't at any time, mate.
You mustn't expect to buy at ATH, which means it will be difficult to get profits then.
Everyone must expect to buy at the lowest price, and it should be in the bearish season.
But for altcoins, it still has a fairly high risk. In the beginning it will provide great returns, but when the altcoin doesn't have any development it will just be trash. make sure you have top altcoins that have good development in the future if you really want to invest in altcoins.
Actually, both altcoins and Bitcoin are high-risk investments. But altcoins are riskier than Bitcoin.
If you are afraid of scam projects or failed projects of altcoins, you are better to choose the top altcoins from trusted projects only. ETH, BNB, TRX, ADA, MATIC, and SOL are some examples of recommended top altcoins.