Consider your resources. If your website traffic has been increasing by 10 percent with blogging alone but you’re now going to start investing in pay-per-click (PPC) ads, you can expect an increase that correlates with the additional spend. If you’re a B2B company, you can expect about a 2.5 percent click-through rate for your ads. The cost of PPC ads is based on the keywords you’re bidding on, who else is bidding on them and how relevant your ads are (known as your quality score). A marketing agency with expertise in demand generation will be able to recommend a budget and set realistic expectations for website traffic based on that budget.
Lets just say that out of the 200 clicks, you received 3 sales, which were tracked with a Facebook conversion pixel. Those 3 sales resulted in $800 in revenue. So your $100 investment just drove $800 in sales. Now, this is simply a generic example , but when you know how to track your ads or other marketing efforts, then you'll know what's paying off and what's not.