>>1832087buy a pair of ISSI stomp pedals to replace the stupid foot retention pedals. Or raceface chesters.
buy a new set of tires once the season is over or your old ones worn out. I suggest Conti 5ks. They are about twice as much as a normal tire but you can really feel the difference.
If you really want to, put $100 a month away in the bank and in 3 years when you have ridden this bike a ton you can upgrade to the absolute newest bike in that $3000 price range- if you so desire.
Your current bike works well as specced so it wouldn't be worth it to upgrade. Just keep this in great shape and save for a new bike years later.
Also buy:
A chain stretch checker tool (less than 10 euro) to check the chain which you replace if it is stretched. replacing a chain on time saves $ because only the chain gets damaged.
Maybe buy a water bottle holder and a nice insulated water bottle like camelback podium. Oh and a bell.