I took the unscored AAMC exam before I did anything else and am so glad I did. I questioned the advice at first, because of what so many people at SDN said about things like free half tests from various companies. It ends up that the advice I got from my big sib and her friends was better than what I was reading here (sorry SDN.) Don't waste your time on the promotional half tests. Start with something from AAMC so you have an idea of what realistic exams are supposed to look like. Only do one AAMC exam, because you'll want to save your other three AAMC exams for the end. Doing that AAMC unscored exam early changed my mindset and helped me zero in on where I needed to improve. I'm talking about both content and the way I was approaching the exam.
Do an SDN search on diagnostic exams and you'll be surprised what you read. There is no such thing, which makes sense because there is no way to ask everything in one exam. Only do exams meant to be FLs.