The c4ds are too sharp,i can clearly see the pixels especially at the edges.
The subject of the image has random white spots,also a crapload of contrast.
Now i wonder: If you follow a tutorial and it says to add contrast,but you see it doesn't turn out well,don't you revert the change?
Tip to improve:
Add contrast only if the image results blurred otherwise.
Make text different: Format it in various ways,typing it plain and simple isn't effective.
I know what you feel when starting a new image:
"I'm not really good,let's throw in a render...some C4Ds and it won't be too bad." <<< wrong!
C4Ds must be used with moderation,if you need something to throw in go for brushes,not C4Ds.