This is referring to the Equestrian Store event/promotion that's typically held around Halloween, though also sometimes at other points during the year. Children come to your shop with part of their costume/outfit and you have to complete it with the piece(s) they're missing. You won't be able to make progress on this trophy until the event/promotion is happening again. Keep an eye on the Spoiler Zone in the Events forum and Howrse's social media to find out about upcoming events/promotions.

you've done some of it, so you would remember the riders store contests. Where we earn pieces of clothing by doing tasks and then put them on customers for points which we spend in the contest store on prizes. You wont be able to get more points for that trophy until we have another store contest. Keep your eyes on the spoiler zone for possible advance notice for future contests.

all of the trophies under the events portion of the trophies can only be worked on during it's promo. right now you can work on the Trip trophy. only exception is the space traveler trophy for catching UFOs.

sorry meant we can work on CARDS trophy not Trip