Where can someone go to find ideas for 70s fancy dress costumes. There are some great sources on the internet. The one you choose depends on what you like. One of the fanciest is a pirate costume with its ruffled shirt, big hat and pantaloons.
You will want to follow the suggested theme the hostess included with the party invitation. Representing horror films requires vampire garb with long black cape lined in shiny red material. Blood and dagger like fingernails polished in red looks realistic. You might want to carry a bat.If you are invited to a theme party, that limits your choices.
For a party theme based on a specific time period, your costume should represent that era. If it is for the old West, you could choose a gunfighter outfit with boots and jeans and a big cowboy hat. Women wore long, homespun gowns and prairie bonnets. Fallen women of the times wore gowns that were colorful and low cut.
One hostess might request costumes be from the sixties era. Girls might select a felt circle poodle skirt with a wide belt, a sweater and saddle shoes with white bobby sox. The boys wore semi dressy pants and button down shirts in plaids or quiet colors. A high school theme might bring cheerleader outfits or football uniforms.
The sixties was the era of the hippie flower children with bell bottom jeans and peasant blouses. Men and women alike wore sandals. Some went barefoot in long skirts with long, flowing hair to match. You could wear a wig with a crown of flowers. A man could wear a wig and a peace necklace over a tunic shirt.
A beach type party would have swim suits of all kinds, from thongs to old fashioned suits for the man with mid thigh length and sleeveless undershirt style tops. Women would wear bathing caps with wild flowers attached and swim suits from the seventies. There would be a mermaid outfit or maybe two. Someone would inevitably bring a surf board.
When you ask where can someone find ideas for fancy dress costumes, there are online stores. One fancy mode of dress was that worn at a Renaissance Fair. The men wore pantaloons and white stockings and shirts or jackets with velvet inserts. The women wore long gowns with bloused sleeves and laced up bodices. The choices are endless.