You'll see a big variance between your Kaplan scores and your real scores, if your experience is similar to that of most people. Kaplan's tests are a lot harder than the real thing, so if you use those tests, ignore the scores. I would suggest taking the Powerprep tests first (download free from mba.com). In fact, do these before going too far in the ETS book because you'll see some of the same questions in both.
Also get the Princeton Review book with the CD. It has a better review of the GMAT than Kaplan, and better strategies. Their tests are more like the real thing, especially the RC questions. The CD has 5 tests on it.
If you want to see average and range of GMAT scores for the top schools, go to
https://www.businessweek.com to see the rankings, and then see their stats. You can also get more info on these schools, including what criteria they consider most important, on
https://www.review.com. From what I've read in the forums, aim for 700+ for Top 10, maybe a little less for Top 20.
Also, one other quick thing - it's "register", not "registrate". Not sure you'd have occasion to use that word in any of your essays, but just in case, you want to be sure to get it right!