I can tell you what worked for me and did not work for a friend:
Oldest DD gave up the sport (3 Day rider for years) after her last horse vetted perfectly then 5 years later developed arthritis and would need to go to a dressage home. She’d sacrificed time and money (probably more than she should have, but how does a parent --or anyone --tell a horse person that?) - she was heartbroken-she called me and told me she sold her horse to a dressage home and would I sell ALL her horse stuff. I offered her a flat sum for everything she had --except her horse trailer which she sold herself.
I took everything and cleaned it, sorted it, and measured. As I did so, I wrote a brief description of each item then carefully photographed everything in a giant “lot” and then in groups of 5 that made sense --bridles, halters, saddles, pads, boots, etc. Her riding clothes I did separately as she was my size and I was still riding. I kept some of her stuff for me and sold the rest at the hunt club.
My thought was that regardless of how I sold her stuff, at some point, I was going to have to clean, measure, describe, and photograph --so just sat down and did it.
Then I listed on Ebay as one giant lot under Horse Tack Lot of Items “Event Rider leaving the sport: dressage, jumping, general equipment.” Within hours I was contacted through Ebay by a woman who was just starting to do 3-Day and wanted to buy EVERYTHING --we discussed price (asked her to make an offer) --we agreed on a price (1K more than I paid DD) and I estimated shipping --and BOOM stuff was gone. I think start to finish, it took me about 8-10 hours to do everything, including shipping --but at that time I was still doing Ebay a bunch (ran out of stuff to sell so only do it about once a year now) and had good idea of how to do this.
I send DD the extra (I debated on that since I did the work of selling, but maybe it’s a mom thing).
Conclusion: Ebay worked for me.
What didn’t work for my friends who tried a similar action at a local tack sale: They had been horse people (training, lessons, breeding etc on a small scale --never more than 4 horses) for 50 years. Decided to sell out and move from IN to WA and take only their one remaining horse and dog with them.
Their local tack sale is massive --Kalamazoo 4-H Tack Exchange --I believe largest in the Midwest with about 1000 vendors --mostly 4-H folks selling and buying used stuff --but a few vendors or various horse stuff --anyway --friends loaded 3 pick up trucks and a flat trailer (one pick up was mine) with all their stuff --uncleaned, still looking like it had been in their barn for 50 years --and rented ONE TABLE at the sale–tried to put 21 saddles, 50 bridles, halters, boots, a tote of bits, crops pads, etc on the ONE TABLE to sell in a sale that lasted from 5-9 PM. As you might guess --disaster. No one was going to dig through dirty tack or unstack 21 saddles to find something useable. Friends had to leave that week, all stuff had to be out of their barn (sold the place) --I was told they ended up dumping or burning everything that didn’t sell. I hope that’s not true, but at that point they were out of options.
The sad part is, two weeks before, they’d had an estate sale and sold all their house hold items —he wouldn’t put the horse stuff in the sale because husband thought they could “make more” at the 4-H sale. I was at the estate sale and heard people tell him they’d come to buy horse equipment . . .he SHOULD have sold it in the estate sale.
If you have a good location, or a friend who has a good location --maybe a “garage sale” type action might be best –
So that’s my experience. Good luck.