So, it's generally recommended that they be on a rodent diet with other foods occasionally added in; don't worry, nothing larger than pinkie mice though. That's all covered in the caresheet.

I think they CAN be good beginner snakes, but if you've never had a snake before I would recommend buying an adult. The babies are so small that they are very easy to accidentally harm, and you really have to keep yourself from instinctively grabbing at them when they try to dart away. Females are also much calmer than males, so if you're looking for a snake that will just chill while you're holding it I think an adult female would be the best choice.