Much depends on time of day and your budget. If it is a morning Mass, you could have lunch or brunch, rolls with sliced meats and cheeses, salads, etc. If it is an afternoon Mass, thing cake and punch, If evening Mass, hors d'oevres or snackie things. Remember that this is not a big gift-giving occasion, more of a religious deal, so gifts of a bible, prayer book, rosary, etc are appropriate.