Membership sites can improve your traffic, growth and even the engagement of your readers. Remember: people who register as members also tend to be loyal . . . and loyal readers are the best readers. It means that they trust you. If you continue to provide great services and products for them, they will continue to pay for their monthly subscriptions.
Have in-depth knowledge in your niche? Package it up into an ebook and sell it on your blog. I'd generally advise against selling it (at least exclusively) on Amazon or Kobo, as you'll probably be able to charge much less. If you've already built up a solid audience, you can probably change anywhere from $5 for a very short one, all the way up to $39+.
Once you setup your account on AdSense you will be given a code to add to your blog. This code will automatically display advertisements on your blog from companies who are part of Google’s advertising network. You may see ads from small companies related to your topic, or you may see ads from large companies that are completely unrelated to your topic.