khutch

There is nothing wrong with upgrading your bike if that is what you want to do. If it were me I would have saved up longer and bought an upgraded model from the get go because that is indeed the cheapest way to get a better bike. But that horse has left the barn in your case so it is just something to keep in mind next time. It might be easier next time too since you now have this bike to ride while you save. Don't get me wrong though, there is nothing wrong with the bike as it is either. It could serve you well without any changes for years.

But that's no fun, is it?! What you do is really up to you. In my case I would start with the pedals. I really like clipless pedals and I am happy with the M540s I put on my Fuji. My preference is for mountain/SPD pedals since the cleats are recessed in the sole of the shoes which make it easier to walk in them when you need to make a stop to grab a burger, etc. If you really like platform pedals there are nicer kinds out there too but the ones on the bike are perfectly serviceable so there is less need to replace them right away in that case.

Unless you simply don't like the style of shifter that is on the bike I don't think you would gain anything by changing them. I don't know if it comes with trigger or twist shifters but if you hate the kind on the bike and really prefer the other kind then there is a good reason to swap them out. If you want to really see an improvement in shifting performance then you would have to do a massive upgrade and even then modern low end transmissions are good enough that you might wonder why you bothered when you are done. You would have to go to something like the 105 series (or whatever is equivalent in the mountain bike range) to have a chance of getting a worthwhile improvement. To get that you would need to swap out the rear cassette, chainrings, both derailleurs, and the shift levers to 105 grade components. My Fuji came with the full 105 kit and it is nice stuff, but I don't know how nice what you have is so I can't promise you that the change would be worthwhile. If your goal is to impress other bike nerds, well the 105 series is pretty much the minimum so it won't impress them it will merely get you into the club.

A more fruitful area of modification is the handlebars. If you find that flat bars work well for you then don't bother. If you want more hand and body positions available to fight fatigue, numbness, and the wind then there are options. Drop bars can be great for a lot of riders though they are larger in diameter than flat bars and require a lot of work and generally expense to put them on a flat bar bike since so many components have to be swapped. Trekking bars are compatible in size so they avoid those problems and still work very well for many people. There are a variety of "moustache" and MTB bars that you could use. And a lot of people find that simply adding some aero bar clip-ons to their flat bars gives them enough hand positions to solve any problems they have with flat bars on long rides. And of course bar ends and better grips can be very helpful too.

Other things are more in the line of accessorizing than upgrading. Maybe there are tires that would work better for your riding. How about a rear rack and trunk bag? Fenders? Lights? Water bottle cages? I've done all that to my Fuji and have been quite happy with the results. I also went with trekking bars and the clipless pedals. You can spend quite enough money accessorizing and the accessories will often give you a lot better bang for buck unless something fundamental on your bike is really substandard (and I think that unlikely on a Cannondale). One of the nicest things I added was the Topeak rear rack and insulated trunk bag. It is a great place to carry tools and tire fixin' gear and as I belatedly discovered halfway through this beastly hot summer it keeps water bottles ice cold for hours whereas a bottle in the bottle cage on the frame is lukewarm after 20 minutes.

You've got a good bike already so choose carefully what you would like to do to it and then enjoy the heck out of it!

Ken