Before i start I want to make sure you dont take anything personally in my post, im just inquiring and trying to put some ideas in.
The problem may not be your gear if even your own guild doesnt want to raid with you as a tank. Im wondering if you have tanked any heroics or older raids like naxx/OS/VoA/EoE or anything... do you have any tank experience?
If your not getting raids maybe its because your skill level just isnt there yet, or not up to par with what they expect or can get from someone else.
IF this is the case then your problem is SMALLER then you think. All you need to do is read up a little and then apply what you read to a few practice runs in some heroics or old raids.
IF this is not the case. then im sorry, and maybe you should try to find a new group to raid with