How do I stop being nervous about rush, Especially as a junior?

[ChioLu]

What to wear:
Contact your Greek life office and ask them. They can probably guide you, specific to your university, so you won't be overdressed or underdressed.
Look up the fraternity website/Facebook pages/Instagram pages and see what the members are wearing. If the events are casual, like a afternoon barbecue or an introductory meet and greet, it's safe to go with a golf shirt and belted shorts. Some universities have casual events until the last (invitational) event.
Further along in the rush process, it's hard to beat a button down shirt and khakis. (And since you're on the west coast, the plaid button down is a staple.)
BUT contact your FSL (fraternity & sorority life) office as we do not know what fashion and Greek life are like on your campus (& you don't need to tell us which university).

[33girl]

Disclaimer: I am old enough to be OP's mom and live in what is admittedly not a cutting edge city for fashion. But a leather jacket and an Apple watch sounds like something the divorced dad I met on match dot com would wear for our date at Bravo Italian Kitchen.