I started penning and sorting on my thoroughbred jumper last year, because one of my western friends needed a teammate. The first few times I went in my English tack, but wore jeans and Dublin boots and a Navajo pad - very wenglish, but I couldn’t figure out what to wear. I’m in MA so not sure if it is more serious elsewhere, but no one cared about my tack. I do now have Western tack, but the used saddle I found that fit my horse is a blinged out barrel saddle, so I still don’t blend in. My horse is also 2 hands taller than all the little quarter horses and loves to do his most dramatic extended trot at the cows, so I’ve given up trying to fit in. Everyone has been so friendly and helpful, and all the cow work has calmed my horse down for everything else.
Now for the tips. Sit back - I think of tucking my tail bone under. I still want to get into my half seat whenever something happens. On my horse this is fine since he has zero cutting moves, but I’ve sat on a few trained western horses and have smacked into the horn when they took off after the cow . Also be prepared to be a little out of control. I don’t mean this in a negative way, but at least the horses I’ve ridden will follow the cow and know what to do. Took a little getting used to as I’m used to riding every stride on my horse. To get used to the saddle, I started with my stirrups basically at the same length I’d use for flatwork then lowered them every few rides. I lost my stirrups a lot at the beginning, I find I need to really think of keeping my weight in my stirrups. I post and have seen that most other riders do the same at a trot and sit the jog. For what to wear, I ordered some bootcut jeans in a longer length than normal, already had cowboy boots, and I do always wear a helmet. I’m usually the only adult in a helmet, but no one has ever commented. I wore sun shirts when I went over the summer, the places I go are very casual and most people were in tank tops or t shirts. Now that it’s cold people are in a mix of sweatshirts and jackets.
Go and have fun. It’s laid back, not expensive, top placings win money. I like it so much that I went probably 10 times this year, compared to 1 hunter show.