What great responses here already. OP, it all starts with a dream, a craving, a desire. Not everyone has that, some only want to jump in the 3’ division and are automatically wary of the bigger jumps. Some look forward to the bigger jumps, and can hardly wait for them to become a reality. Yes, it takes a lot of money, especially these days. Also, a lot of luck, still. The big jumps come easier if you are sitting on the right horse.
I had that craving and announced a similar goal at about 10 years old, on watching my first GP. And yes, was lucky to do that for a while, locally. My mounts were TBs, the first one was purchased from the breeder as a long yearling, and I was 12. Yes, my parents did that, and yes, I survived. I’d been riding since 6, and had a good jumping pony at 11, so not a green kid. Our racehorse trainer family friend broke the horse, and I started riding him as a long 2 year old, just before I turned 13, at home, alone, and we worked out our relationship. And yes, he was a GP horse superstar horse in our area… as it turned out. And I was his pilot. My job was to “learn the course, get on, sit down, shut up, and hang on, and stay out of his way”. I always rode at home, but got lots of help from a variety of local coaches and clinicians. The next two horses who were also successful jumpers, who I didn’t ride quite to that caliber, just to the 4’6 to 4’9 courses, were both purchases off the track. No, I was never one who had a lot of money behind me to buy fancy “made” horses… I had to make my own horses. And my showing was limited to what I could afford, and dependent on getting some prize money to help pay for it all. My horse paid my university tuition fees.
Now that I am old (62 !!! this year), I still play at it, when I can and as I feel like it. Got lucky with my last mount, the last horse I trained as a racehorse turned into a way better jumper than she was ever a racehorse- she surprised me LOL. I thought she was a child’s hunter prospect! Of course, OTTBs aren’t thought of as children’s hunter prospects any more, but hey, that doesn’t occur to me. So she was fun… now retired at 22. And my next mount is telling me that he’s a hunter not a jumper, so that’s gonna be a change for me. And I still have 2 to finish breaking… dunno quite what they are gonna be yet… homegrown TBs, but jumping is in their pedigrees.
I tell you this because these goals are life long… not just short term goals. You do what you can, when you can, however you can, with whatever horse you can find or falls into your lap. That may one day include jumping in the big jumper classes, or it may not. Either way, you go, girl!!!