AAMC exams are gold. I would suggest taking the unscored one first, before any other practice exam. Then do four to five commercial exams. Everyone has a different opinion of which are best. I personally liked EK and TBR exams, finding them very helpful for the style of questions I had on my actual MCAT. Others swear by Altius and NS. It's up to you. If I had the money back then, I would have probably done one from each and used the extra exams in the packages I bought as review. The last three ou take must be AAMC. This is critical. You want the most realistic practice right before the real thing.