I know the application is open on July 15 and most schools are on rolling admissions... but how much would applying two months later hurt my chances of getting in? I won't be able to get everything together until September.
As you stated, the earlier the better. 2 months isn't going to make much of difference in my honest opinion. If you think you are a below average applicant, it is probably better the interview early. If you are a competitive applicant, you're probably good to apply probably anytime before 2 months before their deadline.
So it really depends, but I think you'll be fine applying in September. I applied in December and mid-March and still got interviews at all the schools I applied.
September is fine, although make sure you leave time for some problems that you might encounter, such as reference letters, etc being delayed. I had everything ready in september during my application, but didn't have it completed until two months later because of small things that kept my application on hold. Good luck!
September isn't all that bad. It depends on what you mean by getting all of your stuff together.
If grades are not the problem, I suggest you fill out the applications and send them in along with your transcripts. You can then follow up with letters of recommendations and OAT scores later. I did this with all of my applications in fact.
I was even offered an interview from SUNY before they had received my LOR's or OAT score. When I went for my interview I had taken the OAT a few days prior and just brought my scores with me. I sent in my LOR's about a month after the interview.
Best thing to do is to get your application in early though. Even if it is just the application.