Go buy a ream of paper/ a sketchbook. It is fine to sketch on scratch paper, but it dose not look too good when you can see the print on the other side. The sketches did look good, some were a little Fine art-ish. You could try and show more development within an idea. So maybe sketch the same thing ten times but each time it is a little different. Like draw a coupe, then a wagon, then a convertible, then maybe an SUV all based strongly off the same concept, preferablely next to each other.
Thanks for ur advice, it may help me a lot