Do try to go, if you can. Make the effort–hunting is a blast! I hope you get off on the right foot. There can be a feeling that it’s cliquish and snobby. That depends very much on the hunt. The traditions are there for a reason, and it’s a treat to be part of a well turned out field.
Good suggestions so far to borrow a coat that allows for layering. Hunting dress is simple and classic. Black coat, beige breeches, polished black tall boots, white shirt, black hunt cap. A stock tie is nice, if you can manage. Wear your hair neatly contained, use a clean white shaped (not square, not colored)saddle pad. Simple flat brown tack is the best. Don’t use a white lined bridle or blingy browband.
Dressing appropriately is a sign of respect to the sport, the organizers, and the landowners where you hunt. Perhaps you could arrange to go out on an informal day. Depending on the hunt, a lot of times you can find a tweed blazer at a thrift shop that would be just fine, worn with beige breeches, a shirt and necktie, and black boots and helmet.
Contact the hunt secretary and explain your interest, if that’s not who you spoke to previously. He or she can give you some guidelines and pointers. There is a wealth of info online, especially through the MFHA website. Perhaps you could find a member or two to mentor you. Many hunts request that a new hunter ride as a guest with an established member. Even if they don’t, that’s a terrific way to learn the ropes.
Hunts in the western US can be more forgiving. Our mounted beagle pack here in AZ is pretty informal, and we have so much fun it should be a controlled substance. But I was always troubled by one member who showed up for years wearing a sweatshirt on our formal days. Everyone else had gone to the trouble to put together hunting attire, got up early to iron a stock tie and make sure the horse was clean. She was a nice lady and always welcomed but it was insulting to some of us. We never have had so many members that we sent anyone packing!
In the East, some hunts even have a dress code for hound exercise. Just talk to people who actually belong to the hunt in question. If you don’t get a warm welcome, find another hunt.