From my experience (personal and second-hand), the best bet is to learn the skills for what you ultimately want to do, but be prepared to work in a less ideal setting for quite some time to build experience and earn money while you start your own project on the side in your free time. If you're lucky enough to have investors (parents, friends, people you convince that your idea is worth investing in, etc), then this process speeds up a lot, but the risk is higher.
An example for you would be to learn to be a machinist/welder. Work at a job shop making products for other companies in the area that are in various sectors of the manufacturing industry. You'll learn from your peers, and even the designs of the customers, of how to make stuff cheap, yet bad-a**. You'll earn a reasonable living, and you won't be burned out on your hobby because it'll be different enough to keep you sane. You then use that knowledge and experience (as well as money you've made) to start fabricating stuff on the side for what you actually want to do and sell it on forums, to local enthusiasts, etc. You start to build momentum when people acknowledge the bad-assness of your product and skill set, and eventually, you can transition into what you really love doing and have a nice portfolio to back you up.
I am working to a similar goal myself, and am in the works of getting some ideas made into product. I am using a different route for myself than the example, but it's the same general idea. I wish you good luck, hope my blurb helps a bit! Ha ha
