Dry Ice is Nice and easy to get, It really add mood to the party.
Colored light bulbs are readily available at Lowe's and Home Depot for setting a tone.
As a Host/Hostess, Don't burden yourself with an awkward Costume, Keep mobility a priority when designing your disguise.
Have a few extra and easy to fit masks and costumes available for guests who show up without a Costume.
Food Coloring to liven up the libations Or Small Glow sticks to put in drinks.