Good to see your enthusiasm. This is the perfect time for you to finish off your GMAT because you have just finished your graduation, which means you are still in the study mode. However, most B-schools would require you to have a minimum of 2-yr Post-Grad work-ex. Still finish off your GMAT because your GMAT scores are valid for 5 years, leaving aside some schools in Asia which require more recent scores. Again, it's only after you have worked for few years, will you be able to relate to what you are taught at a B-School.
The Kaplan course
-book is pretty decent, though I personally prefer the Manhattan GMAT
prep coursework for Math, Sentence Correction and Reading Comprehension, and the Powerscore Critical Reasoning Bible
for CR. Also The Official Guide is a must!
You are on the right path, just make sure you get a 700+ GMAT score and a decent work ex, and start working on other requirements of B-schools such as, extra-curricular activities, voluntary work, leadership opportunities in your community etc. A strong application would help you get a good scholarship also!
Also if you get a chance, I suggest you read this book called " The Complete Start-to-finish MBA Admissions Guide", it'll answer a lot of your questions.
Hope this helps!
Kudos are motivating!