How can I get the money to buy a dirt bike and gear?

Ya parents have got the right idea, you want ''it'' you go work for it'' same here paper round saturday job summer job etc. If u have to slog for it you will then appreciate it! Go for it Bro, t'wont kill ya werkin a bit.

I cut lawns , detailed cars and worked at the bicycle shop and earned more than enough to buy my own bikes and gear when I was much younger than you are.

At 14, your are pretty limited in what you can do. It really depends on the legal age you can work in your state. Then, get a job somewhere, work hard, and keep your focus on your goals. That, or make some sort of deal with your parents where they help you get into the sport if you maintain some ultra-high GPA or some other thing. You never know. My parents would always support me in the things I was passionate about even if they didn't like them or understand them. I do the same for my kids. You sound like a motivated kid who knows what it takes to get what you want. Another thing you might want to do is hit up motorcycle/regular salvage yards in your area and explain what you're trying to do. I know a towing company in my town that has a pile of old dead motorcycles behind their building. If you lived locally, I bet they would just give you one. Most riders are suckers for kids trying to get into the sport. You might end up with a bike you could fix up for a really low price. Used gear is always for sale on CL or Ebay too. Just make sure your parents are cool with you finding something. Being sneaky is a sure-fire way to wreck the whole project. Good luck.