there are a lot of potential altcoins in the market. you can look in the coinmarket cap or coin gecko.. those who are in the top 10,20,50, and 100 are the ones worth buying..
You can choose from those top list or depends from how you understand the project that you'll going to invest your money.
but before buying you have to do a research first and understand the use case of every coin.
General rule of investment, you need to make sure that you have full knowledge with the project that you wanted to place your money.
I think I would go with top 10 altcoins rather than 20,50 or 100 because top ten would seems potentially more good than other coins as per the marketcap. So it is ok or worth buying altcoins to generate good profit.
It's everyone's own observation, it's your money that you'll going to stake it's best to place your money where you think you can benefits at all.