I just raced at AutoClub Speedway two weeks ago and have instructed there a lot. You can watch my racing video if you want to see the racing line in the Racing section.
If you haven't been on the track for 25 years, then running all stock will be fine.
While this track is kind of hard on the brakes (Turn 3 and Turn 9), the stock pads will be fine as long as they have sufficient thickness. No specific need for ceramic pads but they can be a nice upgrade. Do be sure to flush the fluid and bleed the lines if this hasn't been done in the past year. A nice upgrade is high temp brake fluid (as long as you're replacing it might as well upgrade for a few more $$).
Cheap tires are a poor investment at the track. You want the best tires, not the worst since even as a novice you'll by running 100+ mph on the NASCAR banking (a racing Boxster will see 135mph). Since your DD tires are new, just run them and then upgrade to a high performance summer tire the next time around if you plan to visit the track again in the future.
The stock wheels are fine. My stock 17" wheels have more than 150 track days without an issue.
Download and read the short book "Race Track Attack Guide - AutoClub Speedway". Its a great primer with photos to show you the racing line.
https://www.amazon.com/Race-Track-Attack-Guide-Speedway-ebook/dp/B00433TC36/ref=sr_1_fkmr0_3?ie=UTF8&qid=1538456075&sr=8-3-fkmr0&keywords=race+track+attack+guide+autocad
Speed Ventures is a great event host and will assign you an instructor who will help you learn the track.
The last thing is to have fun!