It can take a considerable amount of time and effort (not to mention expense) to create a full exhibition of artworks so its wise when setting the date for your opening night to set realistic dates by which you can produce enough works.
As a rule of thumb when creating a mixed exhibition of large, medium and small paintings I try to present between 24 and 30 artworks as a body of work, but the space you will be using for your exhibition, your concept style and how much time you have will all be a factor in how many works you actually need.
When preparing for the exhibition it helps to have a firm idea of the physical dimensions of the space you will be exhibiting in. If possible pay a visit to the exhibition location with your tape measure before you start creating your artworks. This will save you from any nasty surprises when you are setting up your exhibition, when you find that either the artworks don’t fill the space or are too big to fit in.
If you haven’t got enough artworks to put on an exhibition of your own then you might as an alternative consider grouping together with other artists to put on a collective exhibition instead, thereby dimming your star a little in deference to the collective, but also giving you a chance of exhibiting some time soon and sharing the considerable organisation load.