The expression is to gain experience. However, I am not sure what the whole song means. I think it is ironic. She is only 16. She is saying she has no personal experience of jewels, gold, living in posh houses [post code envy] but she dreams about travelling in an expensive car etc.But I could write a post with a different interpretation.
So far as her accent - I had trouble placing it - she did not sound American or Canadian though some of the language was American/international. Other words like ain't and post code are British origin. I looked her up and she is a 16 year old from New Zealand. She does not have the New Zealand accents I have heard - they have a particular way of saying i's and e's. However, I think when people sing their accents are less obvious [there are a few exceptions] Hayley Westenra has a definite kiwi [New Zealand] accent. However, Kimbra who is another young New Zealand singer doesn't have an obvious New Zealand accent. I don't know if it is the way that age group now speaks. In the UK whatever their upbringing many people speak estuary English - not cockney but an accent near to it.
It maybe with Hayley I have heard her being interviewed so know she has a New Zealand accent, I cannot recall whether it is obvious when she sings!
LOL! looks like it's a bit complicated, but l like her accent! Thanks a lot Saffron! ;D