How can I find out which quotes or images I am legally able to use in my journal? Who can I quote?

You will need the permission of the person who originally said or wrote the quote in order to put it in your journal unless it's in the public domain :)

As of January 1, 2020, anything written on or before 1924 can be used in any publication.

"The term “public domain” refers to creative materials that are not protected by intellectual property laws such as copyright, trademark, or patent laws. The public owns these works, not an individual author or artist. Anyone can use a public domain work without obtaining permission, but no one can ever own it." https://fairuse.stanford.edu/overview/public-domain/welcome/

Quotes may also be used if they fall within the Fair Use Act parameters. There can be a bit of a gray area which means you will need to make a judgement call. https://fairuse.stanford.edu/overview/fair-use/what-is-fair-use/

https://www.thegoldenquotes.net/ Is a great site to see and search quotes within the public domain.