Hitting a 560 is not the end of the world. It's actually great that you took the prep test to see where you stand and how much improvement you need to do. I firmly believe that you need to get the basics down first. There is no sense in taking a bunch of CATs or looking over hundreds of problems if you don't understand / remember the concepts. Open the OG11
book and go over the guide. That book has more than just problems in it. If I remember right, it is basically a text book (on a limited scale) of what you need to know regarding the GMAT. Start with covering those areas for DS, PS, and others. You'll need to know how to balance equations and inequalities with ease. You'll need to know simple formulae such as r*t=d rate * time = distance, but GMAT almost always puts a twist on these so the problem is more complex.
Get the GMATClub challenges
. They're only $79 for 925 questions (37 questions * 25 tests) which comes to $0.085 per question. And if you have questions regarding the answers or explanations, you can search for forum for the answer as the question has probably already been discussed, and if you still have questions, or the question hasn't been discussed, just ask and you'll get an answer very quickly.
Best of luck to you.
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.