How can I determine if I need renter's insurance? And supplemental questions.

I don’t own expensive things. The only things that I would miss would be my computer, my iphone, a bit of jewelry, and my wardrobe. Do I need renters insurance for that?

Other questions:

How do I determine how much coverage I need?
Can I get another type of insurance to only cover certain items, and would that be a better choice for me?

Any insurance people out there?