The first couple of shows I did I did cross rails, then 2 foot. Just more hours in the saddle help, build confidence and become a strong rider. Before a show we school the week before then have two or so days before the show to rest, but we ride other horses on the barn. So hours in the saddle I think is the best for confidence
I've gone through the exact same. Almost two years I had a horrendous fall and was beyond terrified to even get on a horse. My hip and my back hurt, and I was in so much pain I could hardly get on my horse. My trainer put me on ponies and then we did vaulting it helped with my confidence and lots more.
When I built my confidence up we started with trot poles than a small jump and built them higher with time. It takes time and you need to find a horse you trust. A couple weeks ago we jumped 3ft and we've jumped a 3ft line. To this day I still get nerves and I feel like I'm going to fall but once you get going it starts to all go away.
I hope this helps with your nerves and good luck