Actually there are two free tests that are considered the best guage of actual GMAT score provided by GMAC, the creator of the GMAT test. Check out
www.mba.com and download their "GMAT prep" software. I would take one of the tests to see where you stand, and then save the 2nd test for after your studies so you can see where you ended.
Everything you need to know about studying and learning can be found on our forum, and we have some awesome deals with our partners. Check out our novice study plan here:
gmat-study-plan-start-your-gmat-journey-80727.html?fl=menuStart to familiarize yourself and good luck! Also, don't be disappointment by your GMAT practice test if you don't like your score, we've seen people make 100-200- even 300 point increases on the forum. So nothing is out of reach! Good luck to you