If you want to avoid blob shoes you’ll want to pay attention to the natural shape of the foot. Following the natural curves along this shape can make it look more filled out.
Another thing that can help is adding a few little details to the shoe. These will all depend on what shoe type you are going for of course. Personally I’m best at drawing sneakers and boots.
Until you are comfortable drawing a shoe type I would also suggest having a reference image handy. This can really help you out if you find your shoes looking off so that you can easily compare between the drawing and image.
A Glitch Named Anti 