'Gonna', 'gotta' and 'wanna' are short forms of talking for the phrases 'going to', 'got to' and 'want to', respectively. You will see them in quotes to imitate in writing the way people actually speak. However, if you are just writing these words, without using them in quotes, they are grammatically wrong. 'Going to' is correct in written English, then, unless you are quoting. Those of you who constantly write 'gonna' will just have to bear up under the extra effort and pain it takes to type the extra three letters. ;-)

I'm going to send you

I 'm gonna send you is absolutely right, its an American english, I am going to send you is British english, So both sentence are right with different regional variation use.

The first is substandard English and should never be used, especially in writing. I cannot believe that other instructors approve of its use. It is not tolerated on standardized tests nor in formal interviews.