the best method to get traffic is to decide upon the best theme on which you want to make the site and then write the best content on the site and then promote the site in the best way whether it is off page or on page optimization with which one can definitely drive good amount of traffic on the site.
All of the activities you mentioned can drive traffic. Keep in mind that you article and comments should be very informative so that people should subscribe you which makes you popular.
When blog commenting make a high content comment that will attract readers to visit your site. Make your comment informative that will help people who can read it.
Like most of the others here have told you, what you are doing is a great way to drive traffic. Just keep doing those things and soon you'll get better. By better, I mean this; you will discover exactly which of those work best (bring the highest response) for your specific offer. Once you get that information... continue doing all the others BUT ramp up your efforts on the most successful method by 10 fold. Go all out. And constantly be on the look out for more sources similar to you most successful resource.
You could also try holding a competition for your readers elating to the blog's niche. Just make sure the prize is a good one!
Another reason is that Google think visitors from facebook are your friends and you have asked them to visit your site and click on your ads.