man something i think uve experimented a bit with here is smudging, i can see it slightly on gaara,
what u need to do is find a stock and some c4d that u think find a render,
make sure theyre all high quality and think about what may look nice with the c4d ur using.
After uve done that, have a look down ur tools and get to know all of them a little bit better, figure out how they work (u dont have to do all but there are some good tools like smudging, blurs, sharpen and blur, dodge and burn for lighting aswell, laeyer effects, opacity, gradiant maps...etc)
Now i would suggest for you to look up Shenron's guide to signature making - photoshop
he makes a really good visual guide for newbies
Basically there are some main things that gfxers pay attention to
- Depth
- Lighting
- Quality
- composition
- Colour balance
- Blend
- Flow
If you keep these things in mind when working you'll be fine
Goodluck!