Welcome Berkay! It looks like you’re making great progress.
There are a few things you could do to improve those models, but the best thing you could do at this point is to make more projects and keep moving forward. I agree that lighting makes a big difference (one of my favorite topics), but I’d suggest mainly focusing on improving your modeling skills right now as that will set you up for even more success later on. Clever lighting and textures can hide a model’s shortcomings to some degree, so making a project that’s just a clay render would be a great next step as a beginner.
If you want a critique on any of these in particular or have questions about using Substance with Blender, feel free to mention it here: https://cgcookie.com/t/655-live-event-with-jonathan-lampel-dec-12th-fps-weapons-and-substance
Keep up the good work!
