You don't need to start a new account. You can start posting hubs anytime after you first opened your account, there is no restriction.
Rating is done based on the quality of hubs publishes, how much interaction you do on Hub pages (like viewing and commenting on other hubs, answering questions, posting questions, participating in forums, taking polls, etc)
More interaction and better quality hubs will increase your rating. However, if your main aim is to earn money through Hub Pages, the rating won't matter.