How do you determine what to sell vs. donate?

I feel weird donating things I could make money off of since I’m poor, but I live in apartment so garage sales aren’t an option. I tried planning some elsewhere and it never panned out.

But I have so much stuff to get rid of and can’t wait for it all to sell!

How do you determine what to sell vs. what to donate? Is it based on a dollar amount you might get from it? When you decide to sell something, how long do you give it before you determine it needs to be donated instead?