legally, you don't have to have insurance to ride a bike.
just understand that you are financially responsible for anything you do on that bike. If you get in an accident, & it's your fault, you'll wish you had insurance.
& I would excpet to pay a minimum of 100+ a month, but I can't say for sure.
I think that a 250 is a great way to start & also takin the MSF course.
have fun & good luck