you track a lot right. I signed up for a TNiA at Pittrace in a couple weeks. Right now im just on as a track tour laps, a few paced laps to get to see it. But They have them each month and if i want to go back in May i want to be prepared. Couple things I'm worried about:
-Oil Pan, stock ej205 style
-tires, probably get some GT Radial SX2's for now
-Brakes, I have stock Legacy GT brakes, 336mm fronts with sliding calipers. pads i dunno, wearever gold ceramic maybe on there now
You won't be doing anything with track tour / pace laps. You need to sign up for an actual HPDE where you have no limits on the track.
I would probably upgrade pads and fluid for your first track day, then depending from there how much more you do it start upgrading things like tires, upgraded oil pick up and etc.