The "I'll just make 100 sites" idea is a popular one that just won't die.
In all honesty, sit down and GRIND GRIND GRIND at a few sites (ideally, one) instead of trying the 100 sites route.
Your site A makes 1$ a day? Great I say!
If you think that site has potential to be your main moneymaker, take the time to sit down and think deeply about how to improve it.
What do your readers need (What type of information, what type of media, etc..)?
How can you present the content in a meaningful way?
How can you aquire content / media? (Ideally, without killing yourself in the process)
What are your competitors doing? What of it is worth stealing / copying / imporving?
What is a good idea that no one in the field doing? Examples: videos, podcasts, high res pictures, games, interactive comparison charts, infographics, etc... Can you provide this?
etc...
Then grind
If the site has no potential, forget about it and move on. Seriously. Drop your work on it and work on a site that has potential. Let it sit and earn its 30$ a month, use that money to pay for links, content, media, etc..
(Actually, you should also do this re-investing if you keep the site)