american english - Which is more appropriate: "I gonna" or "I am gonna"?

to put it straight, gonna stands for going to while wanna stands for want to.

gonna will be used to indicate that something is actually going to happen soon. In the other hand, wanna means I am deciding to do something. It doesn't mean that I have actually planned or scheduled it.

for example:
I am going to see the movie on tuesday's night. (means that I will actually watch the movie.)

I wanna see the movie someday. (means that I would like to see it someday.)