Okay, I'll bite. Keep in mind that I'm currently in the midst of applying myself, so I don't really know how all of this will turn out.
Take your "important" electives before September. Remember that you want your grades on your transcript by the time you submit (as soon after September 1st as you can manage). Important electives include your AI/sub-internship and any away electives if you have a dream school already. Other than that, do things that interest you and you think will help you be a better OB/GYN. I've heard people do Radiology, ICU months, anesthesia, ER, breast clinic/surg, Endocrine, Derm, among others. How many OB/GYN electives you want to do is kind of up to you. I did an Acting Internship and an REI elective prior to applying, and then I did two weeks of MFM and a Family Planning elective after applying (just for the educational experience, not because I wanted it on my transcript).
LORs? Most programs want 3 and will accept 4. There are a lot of theories about who you should get letters from, and I don't really know which theory holds the most weight, so I'll leave that to other people.
As for top programs, you're not going to like this answer, but there is no answer. It is soooo individualized. I am interested in Family Planning, so there are some "top" programs I didn't apply to at all since that is not one of their priorities. Does that make "my" programs better? No, it makes them better for me. There are quite a few competitive applicants from my school this year, and we've interviewed at a lot of the same places. Are our #1s the same? Nope. We're different people with different personalities and different career goals. If you tell us more of what you're looking for, we might be able to tell you some programs that fit that.
Good luck!