I've been observing tennis for about 30 years. We're talking here about learning a consistent, directional, second serve. NOT about telling a pro tennis player how to hit his second serve.
If you don't have a second serve yet, you're still not quite comfortable serving with a continental grip. The conti grip forces you to pronate to hit a flat first serve, and you naturally chop the ball if you don't pronate. Use this chop effect to slice a second serve, same swingspeed, but chop and add slice to the ball.
Once you can hit a sidespin second serve, you start throwing the ball up more over your head, so you add topspin, but that's only after you're confident with a FAST swingspeed.
If you start with a topspin serve, having never sliced, you will lose confidence in your second serve because you never ever swung fast on a second serve and relied on it's spin to slow down the ball and get it in. Right in the middle of your second serve sessions, it will break down totally, and in a match, it will totally break down for sure.
Confidence in the swing speed first, THEN add the topspin / kick component.