Hey, welcome to Mustang ownership. lol The thing is, it's totally up to you. The whole point of a Mustang is that you can do whatever to make it your own.
Now, my personal opinion.. If I were you, appearance wise, I would get fog lights and either gray or black stripes, just to break up the red. Performance wise, Airaid Cold Air Intake, Airaid Throttlebody Spacer (don't get the BBK performance throttle body, I hear there are alot of problems with them sticking shut), and dual exhaust to give it a nice exhaust tone.
1966 Mustang Sprint 200--Wimbledon White
1998 Mustang V6 Coupe--Silver--RIP, Totalled by brother
2005 Mustang V6 Premium Coupe--Sonic Blue