Question about handwritten numbers recognition with limited data set
I suggest you the following:


Adding a little bit of noise such as blurring
Transforming the images. You can rotate or stretch a bit, but make sure you don't change too much to change 6 to 9 or o to 0.


You can look at the following tutorials: 


https://stackoverflow.com/questions/14177744/how-does-perspective-transformation-work-in-pil
http://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_geometric_transformations/py_geometric_transformations.html
http://effbot.org/imagingbook/image.htm