Udimi is a safe place where you can buy or sell advertising.
Here you will easily find other online marketers in your niche with thousands of subscribers.
Here is a detailed tutorial with a video about buying traffic on Udimi
Our sellers provide visitors and unfortunately cannot guarantee any "sale". It all depends on your offer, how attractive it is to the potential customer, what benefits you offer to your audience etc.
We would recommend you to run a few test orders with different sellers and see which seller can provide good results for your offer.