I wouldn't even start with $100 items.
Do some buying to build your feedback and to get a glimpse of the buyer experience. Then sell items which it won't really bother you to lose.
While most people are honest, an obvious newbie will get taken advantage of by unscrupulous buyers.
Did you know you won't get your buyer's payment for 21 days? Do you know that you have to ship before you get that payment? Do you know how to make a PP shipping label and why they are a bargain? Do you understand the entire fee structure? Have you seen your listings on a mobile device?