Nice!
You are now on very slippery slope LOL
The single best mod you can make is to the driver. Get as much seat time as you can and keep getting instructors/coaches for a while.
You should also do as many autocross' as you can as they are just about the single best thing to improve your car control skills. Also look and see if your local PCA or POC does a PDS (Performance Driving School) its not a racing school, but will give you the opportunity to better find where your and your cars limits are. Trust Me , you are far below the cars limits (Me too
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I have been tracking my DD 04 986S for over a year now and am keeping it very bone stock, even though there is a bit of pressure(?) from my PCA club members to go into a prepared class.
I switched to EBC Yellow right before my last track weekend at the Ca Festival of Speed at the Autoclub speedway. 1/2 the course was on the NASCAR SuperSpeedway and the other 1/2 was a road course in the infield. Almost too much fun! The YellowStuff worked great and I was very happy with them, no fade, great stopping power even going from 120 to 35 into a corner.
Motul 600 is a fine brake fluid for your use. ATE 200 is good as well and 1/2 the cost. I switched to Motul 600 this year. Invest in a Motive Power Bleeder, get the one with the metal cap, its worth the few extra $$. It will save you a ton of time bleeding or flushing the brakes and you need to bleed them before every track event and change at least once a year
Tires are probably the only other "mod" you want to look at right now. Rs-3's a pretty good choice, with a few other tires that might be a better choice such as Bridgestone Re-71's
I would look to get a 2nd set of wheels in 17" for track and AX use. A couple of reasons to go with 17" wheels. The number 1 reason, tires cost less in 17" than in 18". I am running 225/45-17 front and 255/40-17 rear on stock wheels
Maybe different brake pads as well for street use as the Yellows may squeal a bit and are dusty. I have EBC RedStuff for my DD pads
I would stay away from suspension mods for the time being, other than maybe putting a Porsche M030 sport suspension. It also may depend a bit on what class you want to run in. At least under our regional PCA rules, you can only do things that were available as a factory or dealer installed factory option for USA spec cars if you want to stay in a street stock class. If you do the M030 suspension, be aware there are 2 versions USA spec and ROW and the ROW may not be "legal"for s stock class.
Get a decent alignment
My recommendation is get as much neg camber front an are rear as you can get. Probuby it will max out at around .8 or .9 deg front and around 1.8 in the back
no toe in the front and a smidge in the back
YMMV
All in all the best way to carry more speed is to keep you foot on the skinny pedal and off the small one. The more your drive on the track , the faster you will get as you learn that you can push your car more than you expected and your cajones get bigger