Facebook ads are very expensive, If you really can have some amazing EPC (Earnings per Click) and afford to pay $1.50 - $6.50 per click (CPC), then go ahead...
That might be true if you're using CPC and not CPM. You can get traffic dirt-cheap. I mean as cheap as 0.01 CPC (Cost Per Click), and I'm talking about adult US traffic here, not international. It is not easy to achieve this. You'd need to use CPM bidding, and have a really high CTR. So let's say you're paying 0.30 CPM, and you have a ctr of 0.500%, that means you're only paying 0.06 per click. If you've constructed your campaign correctly and you're targeting and addressing the proper demographic, you'd be able to get a good CTR and cheap traffic.
I have a $2k daily budget with FB and the best way I've found to spend it is to: Create a Fan Page Force a 'Like' to Get Access to a freebie, discount, etc. Use targeted FB ads to drive visitors to the Fan Page Interact with your fans Make your offer I use a 1:5 ratio of non-sales posts to sales offers This works well because you have effectively pre-sold your fans on your offers. Good Luck!
The 1:5 ratio is good. It is just like email marketing where you don't want to keep pitching sales on every single email.