Can I buy a motorcycle

Grew up riding quads and now I’m 18 and want to buy a motorcycle. My dad, a long time bike rider and used to race moto cross told me he doesn’t think it’s a good idea since I’ve never roden a dirt bike and don’t have the experience. None the less I’m pretty sold on buying a bike within the next couple years and I’m wondering if I should gain experience on a dirtbike first.