The condition column expects a value to evaluate to true or false (this follows the same rules as C/C++ where anything other than false or 0 is true).
You have the right idea I believe. When an outfit is selected, set a flag for that costume (either have a variable for each costume: ‘redDress=true;’, or use one variable with a key: ‘currentDress=“RedDress”;’)
In the condition column, test to see if that variable evaluates to true (you can use ‘redDress’ or ‘redDress==true’ or ‘!blueDress’) or the key you’re looking for ('currentDress == “RedDress”). If the value is false, the option won’t be displayed or used in any default way.