Is it possible to draw rectangles, not triangles? There is not rectangles in PrimitiveType enum...
You make a rectangle from triangles, 2 triangles make one square / rectangle, unless you mean using quads?
I noticed you were using 8 points for a rectangle too, which would make sense if you were using linelist, eitherway with triangles you would only need 6 points (4 if indexed). You can always convert single points to quads (rectangles) using the geometry shader, which is probably better for what you want doing
How are you learning DirectX btw?