prius c wiring upgrade big 1?

i did the big 3 in my old car, now i have a hybrid. i haven't been able to find much info on wire upgrades comparable to the big 3. i plan to run 1/0 awg from the battery negative to the chassis (once i find a terminal that will fit 1/0 awg wire and the tiny battery), what else can i do to improve electrical system performance?

No doubt you are talking about the LV distribution as opposed to the main battery and drive. Keep in mind that performance may be limited by the dc-dc converter capability (akin to a normal car's alternator) and the size of the 12V battery. How do you need to preform the electrical performance? What issues are you having?

None of it is "necessary" in the first place, and even more so NOT, with a Hybrid.   You only need better grounds when experiencing noise with audio equipment. If you don't have issues, then it don't need fixed. Upgrading the battery primary cables will be enough. I did one of those BIG x GROUND upgrades in one of my past cars (2000 Avenger ES), and the negative terminal looked like a chia pet within a month, and wouldn't stop corroding and building up corrosion like that. I removed all the grounds, then it was fine... I will never do that again, and never had to.

i figured it would help w performance; i am in the process of upgrading my stereo. i am not having any issues right now, but i am only running the rear speakers at the moment - i haven't installed the front speakers or the subwoofer. hopefully i won't run into any issues. the existing wire from (12v) battery negative to ground looks to be about 8 awg. i have more than enough 1/0 awg left over to use. it sounds like i shouldn't worry about unless i do have issues?

Put it this way, I only change or repair engines when a problem exists. I do not change it just in case it exists (a do or die competition may be different). [While others got conned by unleaded conversions, I saved a fortune!] You can upgrade later if needed. Keep in mind the limitation of the ~200V to 12V dc-dc converter.