I'll help out with the insurance question.............it depends.
First there are two types. Liability which covers the damage you cause to someone else's property or their bodily injury is number one. This will be the cheaper of the two coverages. There are different limits of liability. For example, 100/300 which is $100,000 per occurance or $300,000 policy limit. 100/300 is middle of the road. You can get up to 500/500 but it probably is not necessary. In some states you are required to carry liability. You will not want to be without liability insurance regardless of the laws of your state.
Next is comprehensive/collision. This covers the cost of repair or replacement of the bike. This will only be a requirement if you finance a bike and it has a lien on it. If you own the bike outright you can choose to do without this but if you total it, there is no insurance to replace it. I carry comprehensive on all my bikes regardless of the presence of a bank lien.
As far as how much it costs, this can vary widely. Some insurance companies rate a bike strictly by engine size. Some rate a bike by type such as cruiser or sport bike. As you might expect, sport bikes can be more expensive and larger engine sizes will mean higher rates. Some insurance companies such as State Farm will only insure a bike if you have your car insured with them. The key here is to shop around. Your age will play a huge factor. The older you get, the cheaper it gets. My suggestion is to buy used and get the liability coverage for sure. Price the comprehensive and depending on the cost decide whether you are willing to gamble with your investment/toy.
There is one other thing to consider and that is insurance on yourself. Most motorcycle policies do not offer any coverage for your own personal injury. Therefore it is imperitive that you have your own health insurance which your parents probably have on you already. Ask and make sure. You should also figure out when you can no longer be on your parents health insurance which will vary depending on where their insurance comes from and whether or not you attend college.
Finally, I think your choice of bikes is a great one. I am 42 and if I had to keep only one bike it would be my WR-250R. I have too much fun trail riding. I have a trials tire on the back and a knobby on the front and it is tons of fun on the twisty pavement as well. Let us know how we can help you further. Most of all, I wish you many years and miles of safe travel on two wheels.