Who will buy what and why?

Today's English lesson came upon me whilst driving in my car earlier today. By some strang reason I came to think of an old Monkees tune, I'm Gonna Buy Me A Dog. And that set my mind spinning...

I'm gonna buy me a dog: plain vanilla, just a statement
I'm gonna buy me a dog: considered a turtle first but they're so boring
I'm gonna buy me a dog: what are you buying?
I'm gonna buy me a dog: I ain't gonna steal it
I'm gonna buy me a dog: no, haven't bought the damned thing yet
I'm gonna buy me a dog: I'm not buying it for my auntie
I'm gonna buy me a dog: not two, definitely not three
And finally
I am gonna buy me a dog: no one can stop me

End of lesson.