Every good sig always has several things in it.
1) A focal point - The point to which attention is first drawn when you see the sig.
2) A light source - Usually just done with a white softbrush. A light source is very often used as a focal point.
3) Flow - A sig has to have a certain direction to it, for example it has to feel like it's going from one side to the other or one corner to the other etc.
4) Realistic depth - Have to find your own way to do that. None of yours have that at the moment. Practice putting effects in front of the render too until you get the hang of it.
5) Original, but easy to read text.
If you make sure every one of those is in your sig at a good quality, then the sig will be improved by a ton.
about ratings.. I'm going to rate them solely based on execution.
1) Won't rate that one, will just comment - never make your render completely transparent. Ever. Also, the text is done very poorly.
2) Same as above. This one has something that is like a light source though, but, it has to be in front of the render, not behind it.
3) This one I'd rank at around 6.5/10. I like what you did with the colors, and there is a minor sense of flow. The "Susemi" text is well placed.
(you want to keep texts close to the middle of the sig) Overall though, the sig is a little plain. No real depth. Would've also been nice if you'd add some more pink to the sig, since you already have it on the tail of the.. cat? It's better for a color to appear more than once, makes it more pleasing to the eye. It's also a good idea to use the eye-drop tool to pick up existing colors from your render, to use them to make effects, the background etc.
4) 7/10. Would've been 8/10 if you didn't use the render in a way that it's outside the background. That is a style that a lot of beginners love using, but you have to make sure, that whenever you do this your render has to be PERFECT. It can not be cut off anywhere (this one's leggs are cut off and the top is cut off a little too). If any part is cut off then it ruins the 3D illusion and makes it all go to waste. I really like the effects you used, it looks very good, the colors are nice too. The carmel text fits perfectly. Overall, if you'd use the render properly then this would be your best work by miles.
5) 6/10 Same faults as above, here the background is a bit plain though, and it's a little chaotic and hard to understand. The orange eyes of the render don't fit at all, and they draw a lot of attention. Should've either changed their color or added more orange to the effects/background etc. Also, the edges of the heart(and other stuff in the background too) in the background seem Low quality, Might want to either erase around the edges with a very low opacity soft brush or blur them a bit.
6) 5/10 The render is awesome(but again - chipped both at the top and bottom) but doesn't fit with the overall sig. The effects @ the background are just blinding and too hard to understand. The INoob text is very poorly placed/made. The rest of the text is not noticeable either. especially the korean one.
Overall, Your style seems to be vector-sigs. I'd suggest looking up some vector signature tutorials, they would help you a lot. Vector sigs have a bit different ground rules, about depth, flow etc. As a major plus though - you like colorful sigs and have a pretty good eye on how to mix bright colors well. Those, if done correctly make a very very good signature.
One more note - About the borders. It's a border for a reason, it has to be the topmost layer (unless if you're making a sig like 4. 5. 6.) meaning DO NOT have any effects changing the border's colors anywhere. (even if it's a 3D style like 4.,5.,6.)
Best of luck on improving =)