Originally Posted by blakcloud

Wheels almost always give you the best bang for the buck when you want to upgrade. These can be expensive so you could always try lighter and more supple tires. Flak Jacket tires are great for not getting flats but can be heavy and dull feeling while riding. I would recommend Compass Chinook Pass if they fit your bike.

Your stem is longer than average, most new bikes come with a 100 mm stem but this isn't a a hard and fast rule. If you want to be more upright look at changing the angle of the stem you have now to something different. Make sure your stem is on top of all available spacers on your steerer tube.

Carbon seat post, not worth it unless your current seatpost is a boat anchor. I would invest in carbon bars and stem before I would invest in a carbon seatpost. Again these are costly upgrades but something you can bring to your next bike if you ever go that route.

Edit: I would think about changing out the square taper FSA crank to something lighter but only when it needs replacing or you can sell what you have. I would actually change the crank before stem and handlebars.