I am thinking of transferring to the top notch institution. I know that GPA is the most important factor but what about the rigor of course? How important is it?
Your college course work generally needs to cover the prerequisites of your major and some general education requirements at your target school.
In theory, there’s no clear way to know the intensity of a course. As ucbalumnus said, complete the major req and as many GE req as possible. Also, if they have honors courses you can take those because it looks good - but even those are relative. My daughter took a handful and all it meant was tacking on a 3-page paper (in one case, going to see the prof during office hours and talking about a topic for ten minutes). But at least it shows commitment.