I had < 250 twitter followers when I started, < 50 blog subscribers. I had some reputation as a Ruby developer from open source work and participating in different things but I would say I had a very small network to start from.
I kept the 'fake' sales page as simple as possible. It was static HTML (written with slim-lang) and pushed to heroku (free hosting). I spent $100 on Adwords to get traffic. That bought ~300 visits which led to ~15 people clicking my 'Buy' button. The page wasn't all that different from what I have now, list the benefits of the product, what buyers can expect, etc.
I didn't pay for Twitter ads. In the beginning people retweeted my announcement. Later on readers of the book would share the link to their followers.