A lot of providers like to see at least 18 months between c/s and VBAC.
I believe that your choice of provider and your provider's commitment is one of the most important factors in VBAC success. Time between pregnancies is something that can control. If you aren't pregnant yet, it is a good idea to aim for that spacing. Finding a supportive provider can be difficult and the 18 month spacing is a very common requirement. Even if someone agrees to take you on with less time between pregnancies, they may not be as comfortable and may not work with you as well towards the end of the pregnancy and in labor which can effect your success.
If they are nervous they may be more likely to push a c-section towards the end, put time limits for going into labor on your own, push induction, be more restrictive during the labor, be quicker to declare failure to progress, etc. during labor and move for the c-section. Now, you can try to fight your way through that, but it is better if you don't have to. Some might argue that if the spacing is important to the provider, the provider isn't truly supportive, but in many places in the country, you just don't have a lot of choices so if you aren't pregnant already, there are benefits to waiting a few more months.