Mr. Gatsby treated any minor event as a great party, so you should get prepared in advance. Create your surroundings and move to another era: the interior, clothes of your guests, music… Everything should comply with your idea!
Invitation cards. Inform your guests in advance! Create some electronic invitations or send cards by post (they will add some spice!), or you can hand them personally. The main thing is to recreate the Great Gatsby’s epoch. Be sure to specify the dress-code of the party; it would be nice to attach an explanatory note to the main 1920’s fashion trends.
Decorations. Make it shine! Put more bright garlands, sparkling floral arrangements. Probably you will be lucky to find a couple of classic English chairs or a sofa.
Eats and drinks. Offer your guests a wide range of cocktails (alcoholic and non-alcoholic) and snacks. Drop an idea of a feast and arrange a buffet table with refreshments.
Music. Jazz, jazz and just jazz. You can create a track-list in advance or invite a jazz band that will create an unique atmosphere!
Dancing. It would be great if you learn with your guests some basic movements of Charleston or Foxtrot, the popular dances of the 1920’s. You can do it during the party, however someone should master those movements in advance.
And the most important elements are sincere smiles and unconstrained laughter. Have a nice party!