Why are you in a rush to leave? Is your home life ok? I ask because it is much easier to save when you live with your parents than when you move out on your own. Do you have a job prospect in the area in which you want to move? If not, that might be something else you look in to.
If circumstances allow, I say stay until you have enough saved to purchase a home. If buying doesn't appeal to you save until you have a minimum of 3 months or more saved for living expenses. Home, gas, car, bus, food, utilities etc.
I just don't want you to jump out too soon.
I just realized that what I wrote doesn't make my point all too clear, I apologize. I mean "take the leap" AFTER I turn 18. My parents won't let me leave until I'm 18, anyways. But I meant should I wait a few months after turning 18, or just go out and do it as soon as I can?