Good for you - you have already worked out what so many other fail to spot. Blogging is about the content - if its great, original, useful and interesting then people will read it. They will tell their friends, they will post links for your blog on their blog. Write a great blog and the promotion happens naturally.
Too many people are blogging trying to make money, most of them are bound to fail as they focus all of their efforts on trying to make money rather than creating a great blog.
I would just like to add that I dont practice what I preach - my blog isn't anything special, but I enjoy doing it and around 50% of my content is original and written by me.