This is only my personal experience, but I was also waitlisted at 4 places the first time I applied. This year, I got 4 acceptances!
The first time I applied, I was working in basic science research. After an unsuccessful cycle, I quit and started a clinical job. I didn't change much of my personal statement, maybe some minor revisions, and didn't have too much more to add to my activities, other than my new job and some clinical research. Did some editing, but content was nearly the same. All letters of rec stayed the same, but I submitted a new one from my new job. (fyi, I had some volunteer clinical activities previously, but not paid)
I think if you do end up having to reapply (which I hope is not the case!!!), it's really important to create a narrative. For example, "I was lacking in this area before, but now I have more confidence in XYZ." It seems like my interviewers valued this kind of reflection. imo, it would be better to try a new activity/job as opposed to just getting more hours in your existing activities. It's more conducive to demonstrating a growth mindset.