The various guttersnipes working for Fagin could make for fairly cheap costumes. Some old clothes (or cheapy Primark ones) made to look grubby would work nicely. I had an old pair of leggings I slit at the bottom to make them flap, then a cheap shirt I got all grubby, a simple waistcoat made from some fabric I had lying about = instant ragamuffin. Smudges on my face and a rough cap topped it off.
I bought a thick leather choker and a thin laced one from Primark. I sewed the lace on onto and then to add a finishing touch I attached some mini lamas to the choker which I bought of ebay. I added these as the movie is about Yzma turning the emperor into a lama so I though this would add some fun and a bit of the film into my costume.