First off, welcome to FlyerTalk.
Now, your questions could fill volumes...so you need to answer some questions before any of us can offer to help. I'm sure I'll forget a few, but others will pick-up on this topic also.
1. Do you have an airline preference, or member of any specific FF programs? If not, you definitely want to join 1 or more to maximize your earning potential.
2. Based in Chicago, your obvious choices would seem to be UA or AA, but not totally necessarily.
3. What cities will you be travelling to? With airline alliances & geographics, this could make a difference which 'primary' or 'secondary' airline you choose.
4. How big a factor are expenses? It sounds like you may be able to split it up into a few trips, taking advantage of
Saturday stays for better fares.
5. You say your itinerary is flexible. Does that mean the time is flexible or when you visit certain cities, or both?
I could probably ask about 10 more questions to help qualify your request, but won't. It might only confuse you more...
Some of these basics will help to formulate a strategy for you. More details will follow your responses.