How to behave at a gala reception ?

Hello !
Tomorrow I will be attending a gala reception organized by my university. It’s a really important reception and the dress code it’s pretty strict.
That’s my first event of this scale, I’ve never been to a wedding and I am not used wearing a dress with fancy shoes and full make up.
How do you do in such situation ? I am super stressed about doing something I shouldn’t.
Thanks in advance