Buying traffic is not advisable. If your site is new, you can try adwords or similar ones but it is always better to optimize your site for search engine traffic.
Nope buying traffic has absolutely no advantage . The only thing you get is a 0.001% that your website interest one of the people looking at your website . But in most cases bought traffic comes from bots so it is just a gigantic waste of money .
some people are providing adsense proof traffic, I don't think this should be good for your adsense account.
you can buy advertising, but not buy traffic for adsense. if you buy traffic, you can send it to a landing page without adsense code ,then ok.
If you are buying to promote your products then it will be ok. If send traffic to a website having an adsense code then it bring problems for you and don't let your adsense account get banned.
One of adwords terms states that you can not invite visitors to your website in exchange of any type of incentive. Almost all of the cheap guaranteed visitors systems do the same thing in one way or other. Most of them bring traffic to your website in frames and in iframes. means 1 website which contains 1000 iframes is when opened all the 1000 websites contained in iframes count 1 pageview, no matter they are not even visible.