you have a lot to learn but that's what practice is for!.
first of all too many renders! renders are the images i.e. fabregas etc.
2. cropping! cropping is getting the polygon tool and cutting the shape out then pasting it in.
3. the background: you just got a wallpaper of an arsenal badge.
4. the images are squashed, if you want to resize them CTRL + T and hold Shift and drag the corners.
5. add effects to your render, duplicate it a few times and try things like filter>blur>gaussian blur etc.
6. add textures, go to deviantart.com and search textures and download them and put them in your image, set the layers to screen.
7. text-put text in your sig, go to dafont.com for texts to download.
8. follow tuts (tutorials) on PC and google photoshop tuts.
hope this helps