Forget QR codes they are pretty useless IMO.
Ads work really well but don't try and target the masses and pay a cheap CPC, this is where the majority of people go wrong, they think if I can get a CPC of 10-15p that's a good thing, but these people might not be targeted, and targeted traffic is the only type of traffic you want.
If I owned a financial advisory, would I want a 10 year old landing on my website? No! I would rather spend ten times as much as have a 45 year old semi-retired individual who might have "Liked" the FSA page or something similar.
Not all traffic is created equal!!!