Etymological note for English and Americans. "Rolled in the dubs" means "rolled in the puddles", and "cadged mony subs" means "cadged many loans".
"Sub" is an abbreviation of the term "subsistence payment" which was the money which casual building workers would receive on the first Friday after they started work, to tide them over until the following Friday, when they would be entitled to their first week's wages.
Interestingly, in America, if you refer to a "sub", the first thing that comes to most peoples' minds is a MacDonalds type concoction consisting of a long bread roll with various types of meat filling. Maybe the term has spread to the UK by now.
The one phrase in "Star o' the Bar" that puzzles me is "straes in the wind". I have never heard anybody in Scotland pronounce "straws" as "straes", (except when singing this song) and when I sing the song I have to admit I sing "straws in the wind". I could understand "stra's in the wind".
While we are at it does anybody in Scotland really pronounce "blind" to rhyme with "wind" except in this song?
Maybe this is a localised pronunciation native to Tranent, where Davie lives.