Default Help on system restore after unsuccessful rooting

Hi guys, I'm new to XDA and I'm sorry if this is in the wrong section or if any thread already exists.

Alright, I own a Samsung Galaxy Tab 10.1v (GT-P7500) and yesterday I set my mind on rooting it. I checked several guides and saw that what almost everyone told was to use Odin3 to be able to use Clockwork mode and root it through flashing.
Well, I downloaded the zip and the recovery and everything seemed to be perfectly fine until, after flashing and booting the tablet I had no root access. Tried several apps for it (from a terminal to a root checker, and yeah, I know I didn't need to do it).
Anyway, after checking a bit I discovered that the su file nor the busybox didn't appear in the root folder (/system/bin o whatever his directory had to be) so I tried to flash it again. Nothing happened so I downloaded some other zips (the first one was like 2MB and the next one I tried was about 300KB), after this the su/busybox files appeared in its location, but when I tried to use the su command in the terminal I got the permission denied message. Used "ls -l /system/bin/su" to see that the permissions were this (if I recall correctly) ---sr-xr-x-.
After tearing my head apart after several hours of investigating and trying stuff I decided to do a factory reset so I could try (I hoped Superuser, su, busybox and all the other files would be erased) to root it again from scratch. Well, my surprise was the one you probably know, the /system files weren't reseted, I still had the Superuser app and all the other files, and su still had the same permissions and whats even more, it was 0KB though I don't know if the first time I tried to root it, it was already 0KB..

Well, this is my story, and if you could throw a bit of light on it I would be grateful.
Thanks in advance

P.S.: Sorry for my bad English