A great performance depends mostly on hard work. Those who passively study and prepare for the GMAT almost never achieve their desired score, nor should they. However, it's great to know that you're ready to take the challenge!
The first step in this journey involves the diagnostic test to see where you generally stand. After that, design an appropriate study plan. Everyone is different, but a popular formula includes:
1. Verbal - Manhattan SC and Powerscore CR.
2. Quant - Manhattan math guides (five in total) and the
GMATClub Tests.
3. OG - Buy all three guides (OG12,
OG Verbal,
OG Quant).
And preparing for a whole year is definitely
NOT recommended. Almost everyone who adopts such a timetable burns out and scores poorly. With no energy left, they give up on a retake. Aim for three to four months instead.
Although you already implied this in your post, I would like to remind you to begin your GMAT studies with a clean slate; don't become distracted by the negative aspects of your past. Today is a new day - the day that you begin your victory over the GMAT, enroll in a great graduate program, meet new friends, and boost your career!
So, good luck! And if you have any further questions, please don't hesitate to ask.