What would help me on my path to becoming a professional skateboard designer?

The stakeboarding and snowboarding industry is a multi-million dollar industry dominated by a small number of manufacturers. To design and manufacture skateboards, you would likely need to either secure a position at one of those existing brands, or develop your own competing high-end skateboard shop.

First, I'll focus on the first option: working at one of the existing brands. I would start by designing skateboards right now. Get experimental. Work on different styles. You can start with something as simple as pen and paper, but you should start building your design toolkit to include the common tools of modern graphic design. If you take some graphic design courses, audit a graphic design course (just find a course at a local college, show up at the right time, and ask the professor if they are okay if you sit quietly in the back), or find a graphic designer who can mentor you, then you should be able to start picking up the common graphic design tools to make high-quality vector-graphics. You need to recognize that it takes true talent to be hired by one of these companies - there aren't many of them and they don't hire many designers. Start making your list and doing your research. For example, Element is based in Irvine, CA, and does all of its designs in-house. They're likely going to want to hire someone who has a design background and provides them with a portfolio of board deck designs.

Second, I'll explore the second option: developing your own brand and running your own shop. This is a whole different course of action. There's nothing stopping you from doing your own research, designing your own decks, and even contracting the manufacturing out to dedicated skateboard manufacturers (you can even do a google search to find some of them). The biggest challenges here are going to be traditional entrepreneurial challenges: how do you get capital to start your business, and how do you get access to your market. You're talking about a retail operation here, so you're either selling the decks yourself with a dedicated shop, or you're going to be fighting to get your decks into the local skate shops, who may already have some exclusive relationships. If you want to understand this market, I would consider interviewing some skateboard shop managers, share your dream with them, and ask them what it would take for them to carry your decks.

A good place to start, going into college is also taking some shop/3d lab classes where you get a chance to work with tools that actually makes boards. I've had friends who bought all the tools needed, laminated their own boards, and laminated their own graphics. You'll also need to be proficient in the adobe creative software to transfer your illustrations into a digital space. There are a lot of independent board builders who sell custom decks out there, and thats a good niche to play in. Being the owner of both production and design will help you understand the full process.