Trading Bitcoin is less risky compared to altcoins but it doesn’t guarantee much gain unless you decide to hold. If you are good enough, altcoins are more profitable trading wise due to the price fluctuations. You can also diversify your portfolio, use the first half for BTC investment and the other for alts trading.
What's the point of going for more gain if you can't guarantee your own asset security? Talk more of if you will survive the market risk that altcoins offer. If there is no experience and the trader is still new to the market, Bitcoin is volatile, but it's a bit more stable than altcoins. Its risk is not the same, and I would rather recommend trading only Bitcoin or trading only Bitcoin if I'm the trader until I'm ready to accept the risk of dealing with altcoins.