It's common not to draw backgrounds in manga panels and instead use effects to convey a particular emotion or atmosphere.
That's perfectly legitimate, in fact it's something that really distinguishes manga from other types of comics. But that doesn't mean you can omit the background all the time.
The best practice is to draw a background for your first panel of every scene and then show it periodically whenever it makes sense; especially when your characters are moving around.
As you can see in the following page, it's perfectly possible to draw a decent manga page without any background whatsoever, but it might feel disorienting and "off".
