Five-Step-Solution for those who find it intimidating to fill a 100-page sketchbook:
Step 4- If you're just starting to draw the figure this may be your first sketchbook. It would be wise to NOT show it to working professionals at conventions.
I understand you want feedback, the thing is most professional comic book artists HATE looking at beginner's work and they're not honest.
A nasty or disingenuous reply from your hero can crush your dreams and your spirit.