Look, that's the gitanos over there in the corner of the square... sitting there all day, drinking beer, playing their guitar, selling drugs... ohhhh, them no-good gitanos....
If one of them approaches you, you must immediately (and drill this so it becomes instinctive, so that you just throw it out without even thinking about it) say:
-¡E amigo, dame un cigarro! or
-¡Amigo! ¿Tienes 50 céntimos?
Very quickly they will understand.