you probably already use this but pinterest is one of my favorite places to get references, or make inspo boards for different projects or just gather inspo for my art style. its completely free as well
(link is my art pinterest board if you want to see how i use pinterest for art)
Itβs honestly still such a great design resource. Especially because you can navigate through so many ideas quickly.
Behance is great but itβs a little less intuitive imo. It has some very specific resources like beautiful annual reports/super corporate high design stuff.
Reallygoodemails.com is great for doomscrolling email designs
There are some good videos from Aaron Draplin
You might find stuff on his website, too.
probably any fundamentals of design book would do the job
Brand New from Under Consideration is a website that looks at case studies of brands. A subscription is $20. I find the critiques helpful in understanding what to look for in design.