Hit Leap is a good traffic exchange. I agree with it because I am customer. But for Adsense safe traffic, do not use Hit Leap. It will kill you soon. And even don't hire freelancers in fiver. They also use Hit Leap, rank boostup, 10khitz.
For Adsense safe traffic, I use only Alexa Master. But I never use their Auto traffic system. I only use their Banner ads and Text ads. Their banner ads are connected with their Adwords account, Bulk url shortener and adhulk I guess. Everytime I advertise my banner, I get new fresh visitors.
But, if you want more traffic, try Rank Boostup. They are in business since 2008!