What is the rule of thumb for amount of food and champagne needed per guest at my wedding reception? Also...?

The wedding and reception is at a venue with a full (pay) bar, and sells pizza and chicken wings, etc. I am providing a sushi platter, g leaf rolls, mini quishes, maybe a gumbo or something in a crock pot? along with wedding cake and I would like to provide champagne. I'm not sure how much I should bring per person. I have 52 rsvp's as of right now. Thanks for any help.