I'm lying low in the leathers, I am, the best that's ever came
Jay is confident in his ability to make money and buy the finer things in life (expensive leather clothing). He brags that he is the best at what he does.
Also, lying low, as in you never know his triumphs.
Reminiscent of the line in “Coming Of Age” of Reasonable Doubt where he tells Memphis Bleek to [let them other niggas get the name, skip the fame].
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