The light upgrades are common and do give the car a meaner look.
When you say upgrade the brakes, do you mean the pads, calipers, discs?
As for the exhaust there are a few options, do you want it louder or quiet.
Quiet option would be the HKS Hi-Power Silent which is a popular choice and is on my wish list
For something louder, i believe there is one called Tanabe
The more you see other cars the more ideas you will get.
Armrest is probably my favourite mod :)