How bad does an unproductive gap semester look? Looking for honest responses.

I am finishing my senior year this fall. After my first three semesters of undergrad I was doing poorly in classes(multiple Cs and a D in bcpm classes), so I took a gap semester. To be honest, I was very unmotivated during the semester and the following summer, I had no work experience or anything at all. The following semester I did very well in classes and got some clinical experience, which led me towards premed. I now have a lot of experience( clinical, research, some volunteer) and expect to finish around a 3.58gpa. I’m taking a year of classes at a cheap four year college near me to get it to a 3.7. However, I hadn’t considered just how bad the gap during undergrad might look on my application, how big of a red flag is this?