Actually it is  a simple question, but in fact, it may be difficult to pick becaus eyou may find many answers fro the mebers. but percsoally, we are all agree that Etherum is the ebst altcoin to buy.
More, you can try to analyze some altcoins such as LINK as the Defi project coin that will probably give you big chance to profit.
But, there are actually some other favorite altcon suhc as XRP and also DOT ..