The ones that pay in copies are not hard to get into but replies do take forever. Most tolerate simultaneous submissions though, even when they say they don't.
I have a friend who is a poet who sends off tons all at once and keeps a file. She gets published a lot that way, but then she is also a really good poet.
I have personal essays, short stories, and poetry in half a dozen or so, maybe more. It gets old after awhile. I mean, it's a lot of work, and then what? No one reads them. If you are going to teach writing or get an MFA it's worth it though.
Best of luck to you.