The best thing for me is to have a silver rag to polish the silver with and if it´s very dirty in the ring, just clean with some soap and water inside with a small brush. Be very careful if it´s a plain ring without texture or pattons, then you only use the polish rag(cloth).
Keep your dry jeweller in small zipbags, that keeps the silver more shiny.
Don´t keep it in the bathroom their is moist air.
If the brass jewellery get dark and some spots on you can clean the piece with lemon or ketchup and then rise with some water.I also use the silver rag (cloth) to polish the brass.
I don´t have soo much experience with copper jewellery, only tried to mix vineger and salt together and then polish careful.