To get down some basics I would start by buying the Kaplan DAT book. This alone will help you to get an average score of like 18-19. For PAT stuff try to look online for some pdf practice exams to just practice it over and over. Also if you have a friend that took Kaplan ask if they can give you the Kaplan pdf practices tests. There are some practice pdf exams like KSF review, which i haven't checked out, but practice questions are necessary to get you thinking and reinforce material. If you can learn by doing problems, (this is the fastest and most efficient way to study), then buy the DAT Destroyer. In it you will find some very tough questions that will really prepare you and comes with explanations. Whatever materials you end up using make sure that you take hard simulated practice exams before you take the real thing. Some of the best programs out there are Topscore and DAT Achiever: both of which are hard and strongly correlate with the type of questions seen on the DATs.
So use Kaplan as a base, Kaplan pdfs if you can get them as practice questions, online practice questions, DAT Destroyer if you want a high score as long as you put in the time and effort, Topscore and DAT Achiever as practices to see how you would fair on the exam both are 3 full length exams.