A Model Stand makes fitting garments much easier, especially if you are patternmaking and making garments for yourself. However, a Model Stand won't solve all your fitting issues if you have a non-standard figure, unless you get one custom made.
If you buy a standard or expandable body form, even if they are the same measurements as your figure (or your model's figure), this doesn't necessarily mean that it will have the same shape. At a minimum, for a model with large busts, some wadding/wrapping will need to be done around the breasts.
See the article on Body Forms for more information and details of where to order personalized Body Forms.