Don't upgrade anything based on our advice. Ride it. You will know soon enough what needs upgrading. Just be frugal. To put money in this bike might not be the best value. But get some use out of it and learn what's good and what's not. You'll know in time whether to keep it or buy a better bike. And when if you buy something else, keep this. You may need a nice bike that is reliable and comfortable and efficient, but you will almost surely need a beater bike as well, a bike that you don't care about if it gets stolen, vandalized or falls into disrepair.