Do you have target schools? The admissions page should give you a place to start--they will tell you what essays are written, how many recommendations you need, and what average GMAT scores for those programs are.
Generally, in the US, first round applications are early October and second round application deadlines are mid December. GMAT prep takes 120-150 hours, and you'll want 10-20 hours dedicated to writing application essays. Plus, you want to give your recommenders as much notice as you can to help them find the time.