If you advertise your blog in your signature on this forum, how many people are going to read your posts? Then how many of them will look at the link of your blog in your signature? How many of them will click on the link to go to your blog? How many of them will click on the ads that you put on your blog? Lets just suppose one hundred visitors visit your one paged blog a day and one out of those one hundred visitors click on one ad (it's the average), you earn .01 USD. Serious!
Even if you put everything on your blog that people get attracted to, you'll not have visitors unless people (all over the world) become aware that the things they take interest in can be found on your blog. For to attract visitors to a blog you have to do internet marketing. One of those internet marketing techniques is to submit your blog in at least Google, Yahoo and MSN search engines and then try to gain highest rank in search results with a specific key word (it's not at all difficult). Just have a look at it to know how many people search for different word on Google per month
. Try different keywords like "Books" "Religion" "Nature" etc.
If you haven't still created the blog then your first step should be to decide what topic would your blog be.
Putting ads on the blog comes later and is just a five minutes job.