I started with a $300 Giant hybrid bike. I rode it for 30,000 miles, about 8 years, before getting a different bike. I did some repairs and some improvements in that time.

I would recommend a similar strategy, buying an inexpensive bike first and then figuring out what you like and need over the course of a year or more. Right now you don't really know what you need. The standard advice of "buy a used bike" is a bit sketchy in your situation because you both don't really know what you need and will be tempted to take whatever you find, and also you may not know how to fit a bike, and again may be tempted to buy a bike that "kinda fits" - an uncomfortable bike really will turn you off.

Honestly, go to a bike shop. Preferably one that sells Giant or one of the other decent but inexpensive lines, as opposed to Specialized/Cannondale exclusive type shops.

FWIW the GMC Denali is kind of a piece of crap. 28s are kind of narrow for generic city riding. I'd go 32s or 35s but that's just my preference. Perhaps the roads in your city are smoother than they are around me.