1) Have Clear Bra installed at the dealership, and install Rally Amor mud flaps as soon as possible if you care about your paint. As said earlier, get the SPT CBE and ask to keep your stock CBE. I'd also get the short throw shifter, SPT boost gauge, auto-dimming rear view mirror/w compass, and trunk subwoofer options as well.
2) If you don't track your car (and don't plan to in the future), swap out the stock Summer tires and install a set of Michelin Pilot Sport Plus A/S tires. Then sell the stock tires to recoup some of the money.
3) Break the engine in per owners manual...keep below 4000 rpms for 3000 miles. When you change your oil for the first time at 3000 miles, go with a good 5w40 synthetic oil (Shell Rotella T6) or Mobil 1 0w40, a Subaru oil filter, and for the heck of it, install a magnectic oil drain bolt (Dimple).
4) Get a tune as soon as the engine is broken in...the stock tune is crap. A good starting point is a Cobb AP.
5) Get thicker adjustable sway bars & rear sway supports (stay away from Whiteline...their $hit rusts fast), Kartboy end links, front shifter bushing, and rear diff bushings, TiC crossmember bushings, Torque Solutions pitch mount & exhaust hangers, Group 'N' transmission mount & rear shifter bushing, and Cusco lower A arm & steering rack braces.
Stay away from aftermarket CAIs (good for Stage 2 and protunes only), blow off valves, front upper strut tower braces, dark tint (20% or darker), and extended warranties.