Having the first step on your opponent is important if you are trying to blow past them either to shoot, layup, or pass. If you use the first step the correct way then you can almost always be able to blow past your defender.
Now most people think when doing the first step is stepping first before the defense is ready. See now that is slightly correct, but there is definitely more to it than just stepping first than you defender.
When you do the first step you want to make sure that you actually step past. Make sure that this step is past their leg. This gives you an advantage when you need to blow right past them.
Now if you are getting too predictable you can just shoulder or eye movement shake them. Fake right first then fake left and go right in the end is one of my favorites. Staying unpredictable and keeping your moves variety will really help you. Body movement and language is very key to pulling off this move.