I don’t do any english riding, but I can tell you from western experience, the saddle makes all the difference.
The hardest part is finding a saddle that fits you AND your horse. It’s pretty easy to find one that fits you.
If you can find one, I would get one like Esmeralda said, one that is flexible and can fit more than one type of body style horse.
"Take the time it takes, so that it takes less time."
"Expect a lot, accept a little, reward often."