"I want to raid but not been given a chance"

You lost me at the title.

You think real raiders are GIVEN anything? You are wrong. They earn it. Most guilds don't recruit tanks but instead promote from within as reliability is a MUST for a tank. As other have said, gear for dps, work towards tanking. Don't be cheap, use the AH if you are really trying to catch up. Do LFR, Do Pugs, Craft some gear. Don't expect handouts unless you can be a very convincing cross dresser on twitch.