With the Austin to Chicago route You have AA, UA & WN (SouthWest). I'd remove WN because they're the most limited of the operators which reduces flexibility is scheduling and irrops. I'd probably go with AA since they have a good schedule and pairing with SPG is a good combination at least to start with. SPG points transfer to many valuable programs ranking it as a high value point.

For cards I'd look at one or both of the AA cards. One is from Citi & the other from Barclays. Citi usually has 1 year free before the annual fee is due but can come with a nice signup bonus and free first bag which can save you a lot of money and time even if your company pays for it.
The more premium cards can earn you big in points with 3x or 5x points for airline purchases but at this time it's best to focus and learn so you don't end up with orphan miles/points.

For hotels sticking with SPG/Marriott might be good to start with for reasons above but many people start with 1 chain to stick with and then for travel outside of that chain use hotels.com to at least get some form of award (1 free night every 10 nights) to again avoid orphan points.

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