If you can tell us what school you got accepted to and what your potential major might be then it might help us to give better advice. On the other hand, if you have no idea whatsoever what your potential major might be then this might be a reason to take a gap year.
I am inclined to agree with @Hippobirdy that taking a gap year and reapplying to top 30 schools is not likely to come out any different than it did this year. There are plenty of students with only one or two or even no B’s in their entire lives who do not get into top 30 universities for undergrad.
However, to me the most likely downside of taking a gap year is that you take a year off and end up attending the same school that you are already expecting to attend. If you have worthwhile things to do during your gap year, this does not seem to be a problem.
You could attend your in-state public school and try to transfer. However, do not count on being able to transfer to a top 30 university in the US. If you do attend your in-state public school, try to do as well there as you can but expect that you are likely to be there for a full four years.