Well, I'd say tell your parents to prepare their pocketbooks!
Back of the envelope costs will include a high 5 to 6 figure horse. Find yourself a BNT or a Not so BNT that has been able to produce results. Riding at Beacon Hill or Heritage Farm would cost anywhere from 2-4k a month for training. You'll need to show at the A, AA, AAA level and it will take several shows to qualify. That will easily run you up 2-3k a show. Don't even get me started on what it cost to maintain one of these beasts.
I say take it in mini steps. Aiming for the Medal and Maclay is a big commitment! I'd try to find a quality trainer that will teach you how to find eight fences with flow and style. Start by trying to qualify for a local or regional Medal. In Northern California we have a lot of them, NorCal Finals are 3'6" but there are smaller ones too like the Almaden which is 2'9". Work your way up the heights, learn and get a great foundation. Work your way up the ratings in shows too, go to 'C' shows, then 'B' shows and eventually 'A' and 'AA'.
USHJA has some interesting "grassroots" programs (and I use the term lightly) like Emerging Athlete's Program. You can look into: EAP Introduction Junior Career
And Medal and Maclay isn't the be all end all or riding either. I had that dream once, and I had the dedication and skill, but no money and pretty much no time. I've found a ton of satisfaction though riding in IHSA when I aged out and riding as an A/O and Adult Equitation rider when I graduated from college.
Best of Luck to you.