People write lists from time to time, but there really aren't universal, formal this many points for this and this many for that critera for judging in ballroom the way there are in skating. (Occasionally some organization - currently the WDSF - will play with the format of their championships in order to shake things up, but that's not relevant to you).
I'd say your placement is more likely to be based on how well presented you are and how well you dance your material, than what your material is. The exception to that would be if you do something clearly unsuitable, or actually against the rules (if you enter a closed syllabus event, though NDCA doesn't have as many of those). Especially for the first time out, simple and repetitive is good. You won't bore the judges, nor if you are focused on doing it right, yourselves.
Be aware that there is a high probability of there being relatively few dancers in your event - you may even end up being the only one, so you might consider entering the event for a younger age group as well or instead (you can dance all the way down to the 18-35 adult group). Sometimes you can guess from results of past years at the same competition, or you might actually know of specific other couples who are going. Also, it is a fairly common at NDCA comps to combine somewhat compatible separate events on the floor at the same time. So it might be you dance uncontested, but at the same time as a pair of over-45 couples's who are being judged against each other, but not against you.
