There is no one easy way to get tons of people to visit your hubs, but there are a lot of little factors or things you can do to help increase your traffic. Social media is one method. Writing hubs that not only provide unique, quality information, but also look good, and have information people are looking for, goes a long way. Write with the reader in mind, what would you type into Google if you were looking for something?
Also be sure to sign up for Google Analytics, and Google Webmaster tools to help manage your hubs and track traffic statistics. Try to write about topics with keywords that are getting a lot of traffic, but don't have much competition.
Right now, since you have 8 hubs, I would suggest focusing on writing around 10 more hubs with good content, nice pictures either that you own, or are properly cited, and good grammar. Quality content goes a long way in getting traffic!