Some good advice there. I'm assuming with your more "race-oriented" bike you won't be doing any winter riding, but if you are then IMHO studded tires are a necessity. Unfortunately the narrowest 700c tire available is 32 mm wide and likely wouldn't fit your Giant.

For me cycling essentials include the aforementioned puncture-resistant tires, tool kit, and lighting. I also require fenders since I ride in all conditions. I don't like to carry anything on my back so I use a rack, pannier, and trunk bag. I have slowly been acquiring cycling-specific clothing, as it does make commuting and riding in general more pleasurable for me. Safety is also paramount so I wear a helmet at all times, use active lighting even during the daylight hours, have a mirror, and use and Airzound Bike Horn.

Lastly I am somewhat anal-retentive when it comes to locking up my bike. I use a sturdy u-lock, plus a heavy chain/mini u-lock combo. At work my bike is parked in a locked, fenced-in compound that is under video surveillance (I also work at a hospital). I still double-lock my bike in case someone neglects to lock up the compound behind them or, God forbid, one of the other users decides to take my bike. I've heard it said that one should spend at least 10% of the bike's retail price on locks, and I think that's sound advice.