True as you say for beginners it is better to invest in the top altcoins because the risks we face are lighter and easier for us to predict, then in the top 10 coinmarketcap is the right choice but you also have to look at the potential of the coin to make it easier to make a profit.
It also depends on market conditions, if the conditions are in a bullish condition, the coins in the top 10 are always good to choose, but if the market conditions are bad, then whatever you choose will be very risky to lose especially if you are impatient and immediately let go of what you already have.