Used items are great as long as they are still in working condition!
Dressage bridle - Preferably black, white piping, can be snaffle or double
Dressage girth - I don't have a horse of my own so medium length would be good so it would fit a variety of horses.
Dressage leathers - Preferably synthetic but leather would be okay, too.
Irons - Just your regular old Fillis unless you have something else.
--I am also on the look out for half pads that raise the back and then another that lifts the cantle or gives wither relief.