It is best to do them all at once.
The cam will need more air which requires bigger ports and throttle bodies to not drop off at high RPM. You can bore out the T stacks, this is what I have. This means you can burn more fuel. See Jeff Higgins' thread "MFI Pump: Open Heart Surgery" for the procedure to richen the mixture as much as you need to get your car to run. You can make a T spec MFI injection pump push as much fuel as an S or RS 2.7 but it is a bit of a stretch and the space cam is not exactly correct but you should not notice a difference in full throttle power. This can save money doing it yourself.
To run the more aggressive cam, you need to be sure your pistons will not hit the valves. This may mean new pistons with relief cuts to clear the valves especially with high domes for high compression ratios. If you have CIS pistons, you may need new ones. Make sure you can run your fuel with the compression ratio you chose. Twin plug is an easy upgrade that is very benefitial to ease detonation.
It is easiest to do all this at once so as not to tear down the engine multiple times.
Provided you have adequate valve/piston clearance, you can do cam, then ports, then pistons.
For brakes, especially S calipers, go to Eric Shea at PMB performance. His username here is Eric_Shea.
Have fun with the car
