The “fundamentals” are those of basic horsemanship. Found in most competitive equine disciplines. If you don’t have THAT, at least, the ability to handle horses, basic grooming skills, some “horse sense”, you are simply “not eligible” to start to learn about training racehorses. It’s not possible. It’s like saying, “I want to go to University, but I can’t read or write”. Do you own a horse? Have you ever touched a horse? Have you already acquired any experience with horses in another competitive equine sport discipline? Respected trainers do not take on green and new employees into a situation where they can learn about training racehorses unless you can truthfully answer “yes” to some of these questions. Yes, there are books you can read, and history to study, but that’s just "book learnin’ ". Books about Phar Lap, Seabiscuit, Storm Cat, D Wayne Lucas, Tom Ivers books. Each has theories and experiences, which may or may not be helpful to your question. This is “light reading”.
When you have the basic requirements of basic horsemanship skills that you now seek, you can look into Godophin’s “Flying Start” program, if you are eligible. You need some basic requirements to even be considered for this program. They ship you around the world, to their training programs and trainers, top class. I believe they let you rake the shedrows, and perhaps clean tack, and you get to watch what happens there. And they judge you as a human while you are there, to see if you are a potential candidate to train to use in their program, in whatever potential job or jobs that you might be suitable for. If you fail to be offered a job by them at the end of the program (most fail- they only take a few), you at least have some basic idea how to be involved in the industry at top levels, and may be employable by someone else, with this experience under your belt. I believe that their “intake” is early in the year, January or February. I know someone who went through this program, and they did not offer her a job. She feels that she got useful training there, useful experiences.
If you do not have the basic requirements to be allowed into this program, or another like it (we had a “groom’s school” at our local racetrack years ago- (which was NOT comparable to Flying Start at all), then you need to start out learning basic horsemanship, horse handling at a local riding stable, how to clean stalls, how to lead and handle and care for quiet riding horses who are probably not going to klll you, how to groom a horse, how to feed and care for a low level athlete. And use that as a stepping stone to move into the racing industry at a later date, as a groom or hotwalker. All the time learning and gaining equine experience. The “Groom’s School” that I mentioned earlier was a program which took young homeless or street people who knew nothing about horses, had never touched a horse, and gave them basic horsemanship skills at a local riding stable, then moved them on to the racetrack, for further experience. Many fell by the wayside, but a few were well suited to the racing industry, learned what they needed to know to be employable at the track, and became part of the racing industry successfully. Getting to know the local trainers and exercise riders, perhaps learning to ride a lead pony and/or exercise racehorses, and, after years of being licensed as a groom or exercise or pony rider, were eligible to write their trainer’s test. Does this give you some idea about what is required to do what you have indicated you want to do?