A normal 3 piece suit.
Smart but formal as it's always good to look clean and kept
If your going to just volunteer just wear normal clothes. Don't go over the top because you really don't have to. If your going for a paid job them you must make an effort and wear something smart.
You would wear smart and clean.
Shirt, tie, skirt and blazer.
Plain casual clothing as you might get your clothes dusty from cleaning gifts
Something casual, clean and presentable should do.
Be of smart appearance.