Here are some details on how to set up your ads to get better deals from FB. An important thing to keep in mind is that the standard system that everybody uses with FB ads is an AUCTION based system. That means, just like in any other auction, if you always raise your hand and outbid everyone else, you'll get the most winning bids, but you probably won't get the best deals.
Translated into our world, this means you'll get traffic, but it won't always meet your ROI goals.
The way to "bid" at the FB auction is by changing the budget and the bid per action. They are both in the ad set settings as indicated in the images here.
So, 3 settings are important here:
1. Select Website Conversion as campaign objective (can only be done when you CREATE a campaign);
2. Select manual bid and enter an amount (this defaults to $30...which is pretty much like raising your hand all the time at the auction) - you also initially select the conversion criteria in ad sets, although you can change that in the ad settings as well.
3. Set the conversion pixel and choose one or more *tracking* pixels in the ad settings.
That is an important thing to note: There is a difference between the CONVERSION objective (which is what is used by FB to optimize the campaign, and you can only choose one for that purpose), and the TRACKING (you can select multiple "conversion pixels" that can have the same or different conversion types - checkout, add-to-cart, lead...etc)
Hope this helps a bit. Now go and test!