Don't feel pressured to jump right into upgrading every component. It is best to just drive the car and see what you break and go from there. You do too much too fast and you can very quickly end up with something that is weaker than stock. The MT10 is extremely durable and depending on your driving style, you may never even have to do anything besides maintenance... or you could break it every time you go out.
As a newcomer to the hobby, you already have a good platform to start with. Spend the money on tools, organization, charger and maintenance items(diff oil, shock oil, grease, tires, etc) early on... That will save you a lot of headache later on down the line. Also remember, just because something breaks, doesn't necessarily mean you need to upgrade that part. Breaking stuff is part of the fun and strategically placed weak points will keep more expensive repairs at bay. There's a balancing act and often times you can created a much more expensive and annoying weak link farther down the line by upgrading the wrong part with the wrong material.
If you have the itch and absolutely need to spend some money on upgrades... wheels and tires are a good place to start. They completely change how a car feels, looks and drives. Probably the #1 most important upgrade for a RTR IMO. Faster steering servo is a good one as well, although id save that for when the stock one goes out personally. If you plan on getting more than one car at some point, a nice radio with multi-model memory is a good idea as well as it can cut down tremendously on the clutter. It is also the connection between you and the car, which makes it a very dramatic upgrade to the experience IMO.