If it all possible, stay under parent's insurance.
Indeed. When I first got a car when I turned 18 (couldn't get a license until then..thanks stupid Arkansas law!) my first year of 25/50/25 (state minimum in AR) coverage was around $1400. Oddly, that's only slightly less than it would have cost if I were a completely unlicensed driver. Yes, you can get auto insurance even if you don't have a license, at least in Arkansas.
After a year, I was able to drop it down to a little under $1200 by switching carriers. It was the third year of being insured that finally brought it down to something resembling reasonable, about $600 a year. Now I pay around $300 a year for 100/300/100.